[java] Support templated servers (#4998)

* [java] Support templated servers

* Deprecate old signature of invokeAPI method

* throw ArrayIndexOutOfBoundsException

* Update modules/openapi-generator/src/main/resources/Java/ServerConfiguration.mustache

* [java] Regenerate samples

Co-authored-by: Jim Schubert <james.schubert@gmail.com>

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaClientCodegen.java

@@ -288,6 +288,8 @@ public class JavaClientCodegen extends AbstractJavaCodegen
         writeOptional(outputFolder, new SupportingFile("manifest.mustache", projectFolder, "AndroidManifest.xml"));
         supportingFiles.add(new SupportingFile("travis.mustache", "", ".travis.yml"));
         supportingFiles.add(new SupportingFile("ApiClient.mustache", invokerFolder, "ApiClient.java"));
+        supportingFiles.add(new SupportingFile("ServerConfiguration.mustache", invokerFolder, "ServerConfiguration.java"));
+        supportingFiles.add(new SupportingFile("ServerVariable.mustache", invokerFolder, "ServerVariable.java"));
         if (!(RESTTEMPLATE.equals(getLibrary()) || REST_ASSURED.equals(getLibrary()) || NATIVE.equals(getLibrary()) || MICROPROFILE.equals(getLibrary()))) {
             supportingFiles.add(new SupportingFile("StringUtil.mustache", invokerFolder, "StringUtil.java"));
         }

modules/openapi-generator/src/main/resources/Java/ApiClient.mustache

@@ -38,7 +38,9 @@ import java.util.Collections;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Arrays;
 import java.util.ArrayList;
 import java.util.Date;
 import java.util.TimeZone;
@@ -63,6 +65,33 @@ public class ApiClient {
   private Map<String, String> defaultHeaderMap = new HashMap<String, String>();
   private Map<String, String> defaultCookieMap = new HashMap<String, String>();
   private String basePath = "{{{basePath}}}";
+  protected List<ServerConfiguration> servers = new ArrayList<ServerConfiguration>({{#servers}}{{#-first}}Arrays.asList(
+{{/-first}}    new ServerConfiguration(
+      "{{{url}}}",
+      "{{{description}}}{{^description}}No description provided{{/description}}",
+      new HashMap<String, ServerVariable>(){{#variables}}{{#-first}} {{
+{{/-first}}        put("{{{name}}}", new ServerVariable(
+          "{{{description}}}{{^description}}No description provided{{/description}}",
+          "{{{defaultValue}}}",
+          new HashSet<String>(
+          {{#enumValues}}
+          {{#-first}}
+            Arrays.asList(
+          {{/-first}}
+              "{{{.}}}"{{^-last}},{{/-last}}
+          {{#-last}}
+            )
+          {{/-last}}
+          {{/enumValues}}
+          )
+        ));
+      {{#-last}}
+      }}{{/-last}}{{/variables}}
+    ){{^-last}},{{/-last}}
+  {{#-last}}
+  ){{/-last}}{{/servers}});
+  protected Integer serverIndex = 0;
+  protected Map<String, String> serverVariables = null;
   private boolean debugging = false;
   private int connectionTimeout = 0;
 
@@ -177,6 +206,33 @@ public class ApiClient {
     return this;
   }
 
+  public List<ServerConfiguration> getServers() {
+    return servers;
+  }
+
+  public ApiClient setServers(List<ServerConfiguration> servers) {
+    this.servers = servers;
+    return this;
+  }
+
+  public Integer getServerIndex() {
+    return serverIndex;
+  }
+
+  public ApiClient setServerIndex(Integer serverIndex) {
+    this.serverIndex = serverIndex;
+    return this;
+  }
+
+  public Map<String, String> getServerVariables() {
+    return serverVariables;
+  }
+
+  public ApiClient setServerVariables(Map<String, String> serverVariables) {
+    this.serverVariables = serverVariables;
+    return this;
+  }
+
   /**
    * Gets the status code of the previous request
    * @return Status code
@@ -626,8 +682,20 @@ public class ApiClient {
    * @return The full URL
    */
   private String buildUrl(String path, List<Pair> queryParams, List<Pair> collectionQueryParams) {
+    String baseURL;
+    if (serverIndex != null) {
+      if (serverIndex < 0 || serverIndex >= servers.size()) {
+        throw new ArrayIndexOutOfBoundsException(String.format(
+          "Invalid index %d when selecting the host settings. Must be less than %d", serverIndex, servers.size()
+        ));
+      }
+      baseURL = servers.get(serverIndex).URL(serverVariables);
+    } else {
+      baseURL = basePath;
+    }
+
     final StringBuilder url = new StringBuilder();
-    url.append(basePath).append(path);
+    url.append(baseURL).append(path);
 
     if (queryParams != null && !queryParams.isEmpty()) {
       // support (constant) query string in `path`, e.g. "/posts?draft=1"

modules/openapi-generator/src/main/resources/Java/ServerConfiguration.mustache

@@ -0,0 +1,58 @@
+package {{invokerPackage}};
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

modules/openapi-generator/src/main/resources/Java/ServerVariable.mustache

@@ -0,0 +1,23 @@
+package {{invokerPackage}};
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

modules/openapi-generator/src/main/resources/Java/libraries/jersey2/ApiClient.mustache

@@ -37,7 +37,9 @@ import java.util.Collections;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Arrays;
 import java.util.ArrayList;
 import java.util.Date;
 import java.util.TimeZone;
@@ -55,6 +57,7 @@ import {{invokerPackage}}.auth.Authentication;
 import {{invokerPackage}}.auth.HttpBasicAuth;
 import {{invokerPackage}}.auth.HttpBearerAuth;
 import {{invokerPackage}}.auth.ApiKeyAuth;
+
 {{#hasOAuthMethods}}
 import {{invokerPackage}}.auth.OAuth;
 {{/hasOAuthMethods}}
@@ -64,6 +67,74 @@ public class ApiClient {
   protected Map<String, String> defaultHeaderMap = new HashMap<String, String>();
   protected Map<String, String> defaultCookieMap = new HashMap<String, String>();
   protected String basePath = "{{{basePath}}}";
+  protected List<ServerConfiguration> servers = new ArrayList<ServerConfiguration>({{#servers}}{{#-first}}Arrays.asList(
+{{/-first}}    new ServerConfiguration(
+      "{{{url}}}",
+      "{{{description}}}{{^description}}No description provided{{/description}}",
+      new HashMap<String, ServerVariable>(){{#variables}}{{#-first}} {{
+{{/-first}}        put("{{{name}}}", new ServerVariable(
+          "{{{description}}}{{^description}}No description provided{{/description}}",
+          "{{{defaultValue}}}",
+          new HashSet<String>(
+          {{#enumValues}}
+          {{#-first}}
+            Arrays.asList(
+          {{/-first}}
+              "{{{.}}}"{{^-last}},{{/-last}}
+          {{#-last}}
+            )
+          {{/-last}}
+          {{/enumValues}}
+          )
+        ));
+      {{#-last}}
+      }}{{/-last}}{{/variables}}
+    ){{^-last}},{{/-last}}
+  {{#-last}}
+  ){{/-last}}{{/servers}});
+  protected Integer serverIndex = 0;
+  protected Map<String, String> serverVariables = null;
+  protected Map<String, List<ServerConfiguration>> operationServers = new HashMap<String, List<ServerConfiguration>>() {{
+    {{#apiInfo}}
+    {{#apis}}
+    {{#operations}}
+    {{#operation}}
+    {{#servers}}
+    {{#-first}}
+    put("{{{classname}}}.{{{operationId}}}", new ArrayList<ServerConfiguration>(Arrays.asList(
+    {{/-first}}
+      new ServerConfiguration(
+        "{{{url}}}",
+        "{{{description}}}{{^description}}No description provided{{/description}}",
+        new HashMap<String, ServerVariable>(){{#variables}}{{#-first}} {{
+{{/-first}}          put("{{{name}}}", new ServerVariable(
+            "{{{description}}}{{^description}}No description provided{{/description}}",
+            "{{{defaultValue}}}",
+            new HashSet<String>(
+            {{#enumValues}}
+            {{#-first}}
+              Arrays.asList(
+            {{/-first}}
+                "{{{.}}}"{{^-last}},{{/-last}}
+            {{#-last}}
+              )
+            {{/-last}}
+            {{/enumValues}}
+            )
+          ));
+        {{#-last}}
+        }}{{/-last}}{{/variables}}
+      ){{^-last}},{{/-last}}
+    {{#-last}}
+    )));{{/-last}}
+    {{/servers}}
+    {{/operation}}
+    {{/operations}}
+    {{/apis}}
+    {{/apiInfo}}
+  }};
+  protected Map<String, Integer> operationServerIndex = new HashMap<String, Integer>();
+  protected Map<String, Map<String, String>> operationServerVariables = new HashMap<String, Map<String, String>>();
   protected boolean debugging = false;
   protected int connectionTimeout = 0;
   private int readTimeout = 0;
@@ -121,6 +192,33 @@ public class ApiClient {
     return this;
   }
 
+  public List<ServerConfiguration> getServers() {
+    return servers;
+  }
+
+  public ApiClient setServers(List<ServerConfiguration> servers) {
+    this.servers = servers;
+    return this;
+  }
+
+  public Integer getServerIndex() {
+    return serverIndex;
+  }
+
+  public ApiClient setServerIndex(Integer serverIndex) {
+    this.serverIndex = serverIndex;
+    return this;
+  }
+
+  public Map<String, String> getServerVariables() {
+    return serverVariables;
+  }
+
+  public ApiClient setServerVariables(Map<String, String> serverVariables) {
+    this.serverVariables = serverVariables;
+    return this;
+  }
+
   /**
    * Get authentications (key: authentication name, value: authentication).
    * @return Map of authentication object
@@ -670,6 +768,7 @@ public class ApiClient {
    * Invoke API by sending HTTP request with the given options.
    *
    * @param <T> Type
+   * @param operation The qualified name of the operation
    * @param path The sub-path of the HTTP URL
    * @param method The request method, one of "GET", "POST", "PUT", "HEAD" and "DELETE"
    * @param queryParams The query parameters
@@ -684,12 +783,36 @@ public class ApiClient {
    * @return The response body in type of string
    * @throws ApiException API exception
    */
-  public <T> ApiResponse<T> invokeAPI(String path, String method, List<Pair> queryParams, Object body, Map<String, String> headerParams, Map<String, String> cookieParams, Map<String, Object> formParams, String accept, String contentType, String[] authNames, GenericType<T> returnType) throws ApiException {
+  public <T> ApiResponse<T> invokeAPI(String operation, String path, String method, List<Pair> queryParams, Object body, Map<String, String> headerParams, Map<String, String> cookieParams, Map<String, Object> formParams, String accept, String contentType, String[] authNames, GenericType<T> returnType) throws ApiException {
     updateParamsForAuth(authNames, queryParams, headerParams, cookieParams);
 
-    // Not using `.target(this.basePath).path(path)` below,
+    // Not using `.target(targetURL).path(path)` below,
     // to support (constant) query string in `path`, e.g. "/posts?draft=1"
-    WebTarget target = httpClient.target(this.basePath + path);
+    String targetURL;
+    if (serverIndex != null) {
+      Integer index;
+      List<ServerConfiguration> serverConfigurations;
+      Map<String, String> variables;
+
+      if (operationServers.containsKey(operation)) {
+        index = operationServerIndex.getOrDefault(operation, serverIndex);
+        variables = operationServerVariables.getOrDefault(operation, serverVariables);
+        serverConfigurations = operationServers.get(operation);
+      } else {
+        index = serverIndex;
+        variables = serverVariables;
+        serverConfigurations = servers;
+      }
+      if (index < 0 || index >= serverConfigurations.size()) {
+        throw new ArrayIndexOutOfBoundsException(String.format(
+          "Invalid index %d when selecting the host settings. Must be less than %d", index, serverConfigurations.size()
+        ));
+      }
+      targetURL = serverConfigurations.get(index).URL(variables) + path;
+    } else {
+      targetURL = this.basePath + path;
+    }
+    WebTarget target = httpClient.target(targetURL);
 
     if (queryParams != null) {
       for (Pair queryParam : queryParams) {
@@ -793,6 +916,14 @@ public class ApiClient {
     }
   }
 
+  /**
+   * @deprecated Add qualified name of the operation as a first parameter.
+   */
+  @Deprecated
+  public <T> ApiResponse<T> invokeAPI(String path, String method, List<Pair> queryParams, Object body, Map<String, String> headerParams, Map<String, String> cookieParams, Map<String, Object> formParams, String accept, String contentType, String[] authNames, GenericType<T> returnType) throws ApiException {
+    return invokeAPI(null, path, method, queryParams, body, headerParams, cookieParams, formParams, accept, contentType, authNames, returnType);
+  }
+
   /**
    * Build the Client used to make HTTP requests.
    * @param debugging Debug setting

modules/openapi-generator/src/main/resources/Java/libraries/jersey2/api.mustache

@@ -151,7 +151,7 @@ public class {{classname}} {
     String[] localVarAuthNames = new String[] { {{#authMethods}}"{{name}}"{{#hasMore}}, {{/hasMore}}{{/authMethods}} };
 
     {{#returnType}}GenericType<{{{returnType}}}> localVarReturnType = new GenericType<{{{returnType}}}>() {};{{/returnType}}
-    return apiClient.invokeAPI(localVarPath, "{{httpMethod}}", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, {{#returnType}}localVarReturnType{{/returnType}}{{^returnType}}null{{/returnType}});
+    return apiClient.invokeAPI("{{classname}}.{{operationId}}", localVarPath, "{{httpMethod}}", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, {{#returnType}}localVarReturnType{{/returnType}}{{^returnType}}null{{/returnType}});
   }
   {{#vendorExtensions.x-group-parameters}}
 

modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaClientCodegenTest.java

@@ -267,7 +267,7 @@ public class JavaClientCodegenTest {
         generator.opts(clientOptInput).generate();
 
         Map<String, String> generatedFiles = generator.getFiles();
-        Assert.assertEquals(generatedFiles.size(), 34);
+        Assert.assertEquals(generatedFiles.size(), 36);
         TestUtils.ensureContainsFile(generatedFiles, output, ".gitignore");
         TestUtils.ensureContainsFile(generatedFiles, output, ".openapi-generator-ignore");
         TestUtils.ensureContainsFile(generatedFiles, output, ".openapi-generator/VERSION");
@@ -340,7 +340,7 @@ public class JavaClientCodegenTest {
         generator.opts(clientOptInput).generate();
 
         Map<String, String> generatedFiles = generator.getFiles();
-        Assert.assertEquals(generatedFiles.size(), 37);
+        Assert.assertEquals(generatedFiles.size(), 39);
         TestUtils.ensureContainsFile(generatedFiles, output, ".gitignore");
         TestUtils.ensureContainsFile(generatedFiles, output, ".openapi-generator-ignore");
         TestUtils.ensureContainsFile(generatedFiles, output, ".openapi-generator/VERSION");
@@ -410,7 +410,7 @@ public class JavaClientCodegenTest {
         generator.opts(clientOptInput).generate();
 
         Map<String, String> generatedFiles = generator.getFiles();
-        Assert.assertEquals(generatedFiles.size(), 23);
+        Assert.assertEquals(generatedFiles.size(), 25);
         validateJavaSourceFiles(generatedFiles);
 
         String defaultApiFilename = new File(output, "src/main/java/xyz/abcdef/api/DefaultApi.java").getAbsolutePath().replace("\\", "/");

samples/client/petstore/java/feign/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/feign/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/feign10x/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/feign10x/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/google-api-client/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/google-api-client/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/jersey1/src/main/java/org/openapitools/client/ApiClient.java

@@ -39,7 +39,9 @@ import java.util.Collections;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Arrays;
 import java.util.ArrayList;
 import java.util.Date;
 import java.util.TimeZone;
@@ -62,6 +64,15 @@ public class ApiClient {
   private Map<String, String> defaultHeaderMap = new HashMap<String, String>();
   private Map<String, String> defaultCookieMap = new HashMap<String, String>();
   private String basePath = "http://petstore.swagger.io:80/v2";
+  protected List<ServerConfiguration> servers = new ArrayList<ServerConfiguration>(Arrays.asList(
+    new ServerConfiguration(
+      "http://petstore.swagger.io:80/v2",
+      "No description provided",
+      new HashMap<String, ServerVariable>()
+    )
+  ));
+  protected Integer serverIndex = 0;
+  protected Map<String, String> serverVariables = null;
   private boolean debugging = false;
   private int connectionTimeout = 0;
 
@@ -168,6 +179,33 @@ public class ApiClient {
     return this;
   }
 
+  public List<ServerConfiguration> getServers() {
+    return servers;
+  }
+
+  public ApiClient setServers(List<ServerConfiguration> servers) {
+    this.servers = servers;
+    return this;
+  }
+
+  public Integer getServerIndex() {
+    return serverIndex;
+  }
+
+  public ApiClient setServerIndex(Integer serverIndex) {
+    this.serverIndex = serverIndex;
+    return this;
+  }
+
+  public Map<String, String> getServerVariables() {
+    return serverVariables;
+  }
+
+  public ApiClient setServerVariables(Map<String, String> serverVariables) {
+    this.serverVariables = serverVariables;
+    return this;
+  }
+
   /**
    * Gets the status code of the previous request
    * @return Status code
@@ -615,8 +653,20 @@ public class ApiClient {
    * @return The full URL
    */
   private String buildUrl(String path, List<Pair> queryParams, List<Pair> collectionQueryParams) {
+    String baseURL;
+    if (serverIndex != null) {
+      if (serverIndex < 0 || serverIndex >= servers.size()) {
+        throw new ArrayIndexOutOfBoundsException(String.format(
+          "Invalid index %d when selecting the host settings. Must be less than %d", serverIndex, servers.size()
+        ));
+      }
+      baseURL = servers.get(serverIndex).URL(serverVariables);
+    } else {
+      baseURL = basePath;
+    }
+
     final StringBuilder url = new StringBuilder();
-    url.append(basePath).append(path);
+    url.append(baseURL).append(path);
 
     if (queryParams != null && !queryParams.isEmpty()) {
       // support (constant) query string in `path`, e.g. "/posts?draft=1"

samples/client/petstore/java/jersey1/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/jersey1/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/jersey2-java6/src/main/java/org/openapitools/client/ApiClient.java

@@ -30,7 +30,9 @@ import java.util.Collections;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Arrays;
 import java.util.ArrayList;
 import java.util.Date;
 import java.util.TimeZone;
@@ -48,6 +50,7 @@ import org.openapitools.client.auth.Authentication;
 import org.openapitools.client.auth.HttpBasicAuth;
 import org.openapitools.client.auth.HttpBearerAuth;
 import org.openapitools.client.auth.ApiKeyAuth;
+
 import org.openapitools.client.auth.OAuth;
 
 
@@ -55,6 +58,19 @@ public class ApiClient {
   protected Map<String, String> defaultHeaderMap = new HashMap<String, String>();
   protected Map<String, String> defaultCookieMap = new HashMap<String, String>();
   protected String basePath = "http://petstore.swagger.io:80/v2";
+  protected List<ServerConfiguration> servers = new ArrayList<ServerConfiguration>(Arrays.asList(
+    new ServerConfiguration(
+      "http://petstore.swagger.io:80/v2",
+      "No description provided",
+      new HashMap<String, ServerVariable>()
+    )
+  ));
+  protected Integer serverIndex = 0;
+  protected Map<String, String> serverVariables = null;
+  protected Map<String, List<ServerConfiguration>> operationServers = new HashMap<String, List<ServerConfiguration>>() {{
+  }};
+  protected Map<String, Integer> operationServerIndex = new HashMap<String, Integer>();
+  protected Map<String, Map<String, String>> operationServerVariables = new HashMap<String, Map<String, String>>();
   protected boolean debugging = false;
   protected int connectionTimeout = 0;
   private int readTimeout = 0;
@@ -112,6 +128,33 @@ public class ApiClient {
     return this;
   }
 
+  public List<ServerConfiguration> getServers() {
+    return servers;
+  }
+
+  public ApiClient setServers(List<ServerConfiguration> servers) {
+    this.servers = servers;
+    return this;
+  }
+
+  public Integer getServerIndex() {
+    return serverIndex;
+  }
+
+  public ApiClient setServerIndex(Integer serverIndex) {
+    this.serverIndex = serverIndex;
+    return this;
+  }
+
+  public Map<String, String> getServerVariables() {
+    return serverVariables;
+  }
+
+  public ApiClient setServerVariables(Map<String, String> serverVariables) {
+    this.serverVariables = serverVariables;
+    return this;
+  }
+
   /**
    * Get authentications (key: authentication name, value: authentication).
    * @return Map of authentication object
@@ -654,6 +697,7 @@ public class ApiClient {
    * Invoke API by sending HTTP request with the given options.
    *
    * @param <T> Type
+   * @param operation The qualified name of the operation
    * @param path The sub-path of the HTTP URL
    * @param method The request method, one of "GET", "POST", "PUT", "HEAD" and "DELETE"
    * @param queryParams The query parameters
@@ -668,12 +712,36 @@ public class ApiClient {
    * @return The response body in type of string
    * @throws ApiException API exception
    */
-  public <T> ApiResponse<T> invokeAPI(String path, String method, List<Pair> queryParams, Object body, Map<String, String> headerParams, Map<String, String> cookieParams, Map<String, Object> formParams, String accept, String contentType, String[] authNames, GenericType<T> returnType) throws ApiException {
+  public <T> ApiResponse<T> invokeAPI(String operation, String path, String method, List<Pair> queryParams, Object body, Map<String, String> headerParams, Map<String, String> cookieParams, Map<String, Object> formParams, String accept, String contentType, String[] authNames, GenericType<T> returnType) throws ApiException {
     updateParamsForAuth(authNames, queryParams, headerParams, cookieParams);
 
-    // Not using `.target(this.basePath).path(path)` below,
+    // Not using `.target(targetURL).path(path)` below,
     // to support (constant) query string in `path`, e.g. "/posts?draft=1"
-    WebTarget target = httpClient.target(this.basePath + path);
+    String targetURL;
+    if (serverIndex != null) {
+      Integer index;
+      List<ServerConfiguration> serverConfigurations;
+      Map<String, String> variables;
+
+      if (operationServers.containsKey(operation)) {
+        index = operationServerIndex.getOrDefault(operation, serverIndex);
+        variables = operationServerVariables.getOrDefault(operation, serverVariables);
+        serverConfigurations = operationServers.get(operation);
+      } else {
+        index = serverIndex;
+        variables = serverVariables;
+        serverConfigurations = servers;
+      }
+      if (index < 0 || index >= serverConfigurations.size()) {
+        throw new ArrayIndexOutOfBoundsException(String.format(
+          "Invalid index %d when selecting the host settings. Must be less than %d", index, serverConfigurations.size()
+        ));
+      }
+      targetURL = serverConfigurations.get(index).URL(variables) + path;
+    } else {
+      targetURL = this.basePath + path;
+    }
+    WebTarget target = httpClient.target(targetURL);
 
     if (queryParams != null) {
       for (Pair queryParam : queryParams) {
@@ -777,6 +845,14 @@ public class ApiClient {
     }
   }
 
+  /**
+   * @deprecated Add qualified name of the operation as a first parameter.
+   */
+  @Deprecated
+  public <T> ApiResponse<T> invokeAPI(String path, String method, List<Pair> queryParams, Object body, Map<String, String> headerParams, Map<String, String> cookieParams, Map<String, Object> formParams, String accept, String contentType, String[] authNames, GenericType<T> returnType) throws ApiException {
+    return invokeAPI(null, path, method, queryParams, body, headerParams, cookieParams, formParams, accept, contentType, authNames, returnType);
+  }
+
   /**
    * Build the Client used to make HTTP requests.
    * @param debugging Debug setting

samples/client/petstore/java/jersey2-java6/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/jersey2-java6/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/jersey2-java6/src/main/java/org/openapitools/client/api/AnotherFakeApi.java

@@ -96,6 +96,6 @@ public class AnotherFakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<Client> localVarReturnType = new GenericType<Client>() {};
-    return apiClient.invokeAPI(localVarPath, "PATCH", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("AnotherFakeApi.call123testSpecialTags", localVarPath, "PATCH", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
 }

samples/client/petstore/java/jersey2-java6/src/main/java/org/openapitools/client/api/FakeApi.java

@@ -103,7 +103,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.createXmlItem", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * 
@@ -162,7 +162,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<Boolean> localVarReturnType = new GenericType<Boolean>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("FakeApi.fakeOuterBooleanSerialize", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * 
@@ -221,7 +221,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<OuterComposite> localVarReturnType = new GenericType<OuterComposite>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("FakeApi.fakeOuterCompositeSerialize", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * 
@@ -280,7 +280,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<BigDecimal> localVarReturnType = new GenericType<BigDecimal>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("FakeApi.fakeOuterNumberSerialize", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * 
@@ -339,7 +339,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<String> localVarReturnType = new GenericType<String>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("FakeApi.fakeOuterStringSerialize", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * 
@@ -402,7 +402,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testBodyWithFileSchema", localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * 
@@ -473,7 +473,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testBodyWithQueryParams", localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * To test \&quot;client\&quot; model
@@ -537,7 +537,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<Client> localVarReturnType = new GenericType<Client>() {};
-    return apiClient.invokeAPI(localVarPath, "PATCH", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("FakeApi.testClientModel", localVarPath, "PATCH", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Fake endpoint for testing various parameters  假端點  偽のエンドポイント  가짜 엔드 포인트
@@ -671,7 +671,7 @@ if (paramCallback != null)
     String[] localVarAuthNames = new String[] { "http_basic_test" };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testEndpointParameters", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * To test enum parameters
@@ -757,7 +757,7 @@ if (enumFormString != null)
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testEnumParameters", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
 
 private ApiResponse<Void> testGroupParametersWithHttpInfo(Integer requiredStringGroup, Boolean requiredBooleanGroup, Long requiredInt64Group, Integer stringGroup, Boolean booleanGroup, Long int64Group) throws ApiException {
@@ -812,7 +812,7 @@ if (booleanGroup != null)
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testGroupParameters", localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
 
   public class APItestGroupParametersRequest {
@@ -999,7 +999,7 @@ if (booleanGroup != null)
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testInlineAdditionalProperties", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * test json serialization of form data
@@ -1073,7 +1073,7 @@ if (param2 != null)
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testJsonFormData", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * 
@@ -1169,6 +1169,6 @@ if (param2 != null)
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testQueryParameterCollectionFormat", localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
 }

samples/client/petstore/java/jersey2-java6/src/main/java/org/openapitools/client/api/FakeClassnameTags123Api.java

@@ -96,6 +96,6 @@ public class FakeClassnameTags123Api {
     String[] localVarAuthNames = new String[] { "api_key_query" };
 
     GenericType<Client> localVarReturnType = new GenericType<Client>() {};
-    return apiClient.invokeAPI(localVarPath, "PATCH", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("FakeClassnameTags123Api.testClassname", localVarPath, "PATCH", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
 }

samples/client/petstore/java/jersey2-java6/src/main/java/org/openapitools/client/api/PetApi.java

@@ -99,7 +99,7 @@ public class PetApi {
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("PetApi.addPet", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Deletes a pet
@@ -169,7 +169,7 @@ public class PetApi {
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     
-    return apiClient.invokeAPI(localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("PetApi.deletePet", localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Finds Pets by status
@@ -236,7 +236,7 @@ public class PetApi {
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     GenericType<List<Pet>> localVarReturnType = new GenericType<List<Pet>>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("PetApi.findPetsByStatus", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Finds Pets by tags
@@ -307,7 +307,7 @@ public class PetApi {
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     GenericType<List<Pet>> localVarReturnType = new GenericType<List<Pet>>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("PetApi.findPetsByTags", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Find pet by ID
@@ -376,7 +376,7 @@ public class PetApi {
     String[] localVarAuthNames = new String[] { "api_key" };
 
     GenericType<Pet> localVarReturnType = new GenericType<Pet>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("PetApi.getPetById", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Update an existing pet
@@ -445,7 +445,7 @@ public class PetApi {
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     
-    return apiClient.invokeAPI(localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("PetApi.updatePet", localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Updates a pet in the store with form data
@@ -517,7 +517,7 @@ if (status != null)
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("PetApi.updatePetWithForm", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * uploads an image
@@ -590,7 +590,7 @@ if (file != null)
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     GenericType<ModelApiResponse> localVarReturnType = new GenericType<ModelApiResponse>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("PetApi.uploadFile", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * uploads an image (required)
@@ -668,6 +668,6 @@ if (requiredFile != null)
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     GenericType<ModelApiResponse> localVarReturnType = new GenericType<ModelApiResponse>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("PetApi.uploadFileWithRequiredFile", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
 }

samples/client/petstore/java/jersey2-java6/src/main/java/org/openapitools/client/api/StoreApi.java

@@ -98,7 +98,7 @@ public class StoreApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("StoreApi.deleteOrder", localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Returns pet inventories by status
@@ -155,7 +155,7 @@ public class StoreApi {
     String[] localVarAuthNames = new String[] { "api_key" };
 
     GenericType<Map<String, Integer>> localVarReturnType = new GenericType<Map<String, Integer>>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("StoreApi.getInventory", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Find purchase order by ID
@@ -224,7 +224,7 @@ public class StoreApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<Order> localVarReturnType = new GenericType<Order>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("StoreApi.getOrderById", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Place an order for a pet
@@ -290,6 +290,6 @@ public class StoreApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<Order> localVarReturnType = new GenericType<Order>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("StoreApi.placeOrder", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
 }

samples/client/petstore/java/jersey2-java6/src/main/java/org/openapitools/client/api/UserApi.java

@@ -95,7 +95,7 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("UserApi.createUser", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Creates list of users with given input array
@@ -158,7 +158,7 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("UserApi.createUsersWithArrayInput", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Creates list of users with given input array
@@ -221,7 +221,7 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("UserApi.createUsersWithListInput", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Delete user
@@ -287,7 +287,7 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("UserApi.deleteUser", localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Get user by user name
@@ -356,7 +356,7 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<User> localVarReturnType = new GenericType<User>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("UserApi.getUserByName", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Logs user into the system
@@ -431,7 +431,7 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<String> localVarReturnType = new GenericType<String>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("UserApi.loginUser", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Logs out current logged in user session
@@ -487,7 +487,7 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("UserApi.logoutUser", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Updated user
@@ -560,6 +560,6 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("UserApi.updateUser", localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
 }

samples/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/ApiClient.java

@@ -31,7 +31,9 @@ import java.util.Collections;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Arrays;
 import java.util.ArrayList;
 import java.util.Date;
 import java.util.TimeZone;
@@ -49,6 +51,7 @@ import org.openapitools.client.auth.Authentication;
 import org.openapitools.client.auth.HttpBasicAuth;
 import org.openapitools.client.auth.HttpBearerAuth;
 import org.openapitools.client.auth.ApiKeyAuth;
+
 import org.openapitools.client.auth.OAuth;
 
 
@@ -56,6 +59,19 @@ public class ApiClient {
   protected Map<String, String> defaultHeaderMap = new HashMap<String, String>();
   protected Map<String, String> defaultCookieMap = new HashMap<String, String>();
   protected String basePath = "http://petstore.swagger.io:80/v2";
+  protected List<ServerConfiguration> servers = new ArrayList<ServerConfiguration>(Arrays.asList(
+    new ServerConfiguration(
+      "http://petstore.swagger.io:80/v2",
+      "No description provided",
+      new HashMap<String, ServerVariable>()
+    )
+  ));
+  protected Integer serverIndex = 0;
+  protected Map<String, String> serverVariables = null;
+  protected Map<String, List<ServerConfiguration>> operationServers = new HashMap<String, List<ServerConfiguration>>() {{
+  }};
+  protected Map<String, Integer> operationServerIndex = new HashMap<String, Integer>();
+  protected Map<String, Map<String, String>> operationServerVariables = new HashMap<String, Map<String, String>>();
   protected boolean debugging = false;
   protected int connectionTimeout = 0;
   private int readTimeout = 0;
@@ -113,6 +129,33 @@ public class ApiClient {
     return this;
   }
 
+  public List<ServerConfiguration> getServers() {
+    return servers;
+  }
+
+  public ApiClient setServers(List<ServerConfiguration> servers) {
+    this.servers = servers;
+    return this;
+  }
+
+  public Integer getServerIndex() {
+    return serverIndex;
+  }
+
+  public ApiClient setServerIndex(Integer serverIndex) {
+    this.serverIndex = serverIndex;
+    return this;
+  }
+
+  public Map<String, String> getServerVariables() {
+    return serverVariables;
+  }
+
+  public ApiClient setServerVariables(Map<String, String> serverVariables) {
+    this.serverVariables = serverVariables;
+    return this;
+  }
+
   /**
    * Get authentications (key: authentication name, value: authentication).
    * @return Map of authentication object
@@ -654,6 +697,7 @@ public class ApiClient {
    * Invoke API by sending HTTP request with the given options.
    *
    * @param <T> Type
+   * @param operation The qualified name of the operation
    * @param path The sub-path of the HTTP URL
    * @param method The request method, one of "GET", "POST", "PUT", "HEAD" and "DELETE"
    * @param queryParams The query parameters
@@ -668,12 +712,36 @@ public class ApiClient {
    * @return The response body in type of string
    * @throws ApiException API exception
    */
-  public <T> ApiResponse<T> invokeAPI(String path, String method, List<Pair> queryParams, Object body, Map<String, String> headerParams, Map<String, String> cookieParams, Map<String, Object> formParams, String accept, String contentType, String[] authNames, GenericType<T> returnType) throws ApiException {
+  public <T> ApiResponse<T> invokeAPI(String operation, String path, String method, List<Pair> queryParams, Object body, Map<String, String> headerParams, Map<String, String> cookieParams, Map<String, Object> formParams, String accept, String contentType, String[] authNames, GenericType<T> returnType) throws ApiException {
     updateParamsForAuth(authNames, queryParams, headerParams, cookieParams);
 
-    // Not using `.target(this.basePath).path(path)` below,
+    // Not using `.target(targetURL).path(path)` below,
     // to support (constant) query string in `path`, e.g. "/posts?draft=1"
-    WebTarget target = httpClient.target(this.basePath + path);
+    String targetURL;
+    if (serverIndex != null) {
+      Integer index;
+      List<ServerConfiguration> serverConfigurations;
+      Map<String, String> variables;
+
+      if (operationServers.containsKey(operation)) {
+        index = operationServerIndex.getOrDefault(operation, serverIndex);
+        variables = operationServerVariables.getOrDefault(operation, serverVariables);
+        serverConfigurations = operationServers.get(operation);
+      } else {
+        index = serverIndex;
+        variables = serverVariables;
+        serverConfigurations = servers;
+      }
+      if (index < 0 || index >= serverConfigurations.size()) {
+        throw new ArrayIndexOutOfBoundsException(String.format(
+          "Invalid index %d when selecting the host settings. Must be less than %d", index, serverConfigurations.size()
+        ));
+      }
+      targetURL = serverConfigurations.get(index).URL(variables) + path;
+    } else {
+      targetURL = this.basePath + path;
+    }
+    WebTarget target = httpClient.target(targetURL);
 
     if (queryParams != null) {
       for (Pair queryParam : queryParams) {
@@ -777,6 +845,14 @@ public class ApiClient {
     }
   }
 
+  /**
+   * @deprecated Add qualified name of the operation as a first parameter.
+   */
+  @Deprecated
+  public <T> ApiResponse<T> invokeAPI(String path, String method, List<Pair> queryParams, Object body, Map<String, String> headerParams, Map<String, String> cookieParams, Map<String, Object> formParams, String accept, String contentType, String[] authNames, GenericType<T> returnType) throws ApiException {
+    return invokeAPI(null, path, method, queryParams, body, headerParams, cookieParams, formParams, accept, contentType, authNames, returnType);
+  }
+
   /**
    * Build the Client used to make HTTP requests.
    * @param debugging Debug setting

samples/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/api/AnotherFakeApi.java

@@ -96,6 +96,6 @@ public class AnotherFakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<Client> localVarReturnType = new GenericType<Client>() {};
-    return apiClient.invokeAPI(localVarPath, "PATCH", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("AnotherFakeApi.call123testSpecialTags", localVarPath, "PATCH", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
 }

samples/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/api/FakeApi.java

@@ -103,7 +103,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.createXmlItem", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * 
@@ -162,7 +162,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<Boolean> localVarReturnType = new GenericType<Boolean>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("FakeApi.fakeOuterBooleanSerialize", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * 
@@ -221,7 +221,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<OuterComposite> localVarReturnType = new GenericType<OuterComposite>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("FakeApi.fakeOuterCompositeSerialize", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * 
@@ -280,7 +280,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<BigDecimal> localVarReturnType = new GenericType<BigDecimal>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("FakeApi.fakeOuterNumberSerialize", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * 
@@ -339,7 +339,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<String> localVarReturnType = new GenericType<String>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("FakeApi.fakeOuterStringSerialize", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * 
@@ -402,7 +402,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testBodyWithFileSchema", localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * 
@@ -473,7 +473,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testBodyWithQueryParams", localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * To test \&quot;client\&quot; model
@@ -537,7 +537,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<Client> localVarReturnType = new GenericType<Client>() {};
-    return apiClient.invokeAPI(localVarPath, "PATCH", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("FakeApi.testClientModel", localVarPath, "PATCH", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Fake endpoint for testing various parameters  假端點  偽のエンドポイント  가짜 엔드 포인트
@@ -671,7 +671,7 @@ if (paramCallback != null)
     String[] localVarAuthNames = new String[] { "http_basic_test" };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testEndpointParameters", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * To test enum parameters
@@ -757,7 +757,7 @@ if (enumFormString != null)
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testEnumParameters", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
 
 private ApiResponse<Void> testGroupParametersWithHttpInfo(Integer requiredStringGroup, Boolean requiredBooleanGroup, Long requiredInt64Group, Integer stringGroup, Boolean booleanGroup, Long int64Group) throws ApiException {
@@ -812,7 +812,7 @@ if (booleanGroup != null)
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testGroupParameters", localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
 
   public class APItestGroupParametersRequest {
@@ -999,7 +999,7 @@ if (booleanGroup != null)
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testInlineAdditionalProperties", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * test json serialization of form data
@@ -1073,7 +1073,7 @@ if (param2 != null)
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testJsonFormData", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * 
@@ -1169,6 +1169,6 @@ if (param2 != null)
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testQueryParameterCollectionFormat", localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
 }

samples/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/api/FakeClassnameTags123Api.java

@@ -96,6 +96,6 @@ public class FakeClassnameTags123Api {
     String[] localVarAuthNames = new String[] { "api_key_query" };
 
     GenericType<Client> localVarReturnType = new GenericType<Client>() {};
-    return apiClient.invokeAPI(localVarPath, "PATCH", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("FakeClassnameTags123Api.testClassname", localVarPath, "PATCH", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
 }

samples/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/api/PetApi.java

@@ -99,7 +99,7 @@ public class PetApi {
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("PetApi.addPet", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Deletes a pet
@@ -169,7 +169,7 @@ public class PetApi {
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     
-    return apiClient.invokeAPI(localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("PetApi.deletePet", localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Finds Pets by status
@@ -236,7 +236,7 @@ public class PetApi {
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     GenericType<List<Pet>> localVarReturnType = new GenericType<List<Pet>>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("PetApi.findPetsByStatus", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Finds Pets by tags
@@ -307,7 +307,7 @@ public class PetApi {
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     GenericType<List<Pet>> localVarReturnType = new GenericType<List<Pet>>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("PetApi.findPetsByTags", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Find pet by ID
@@ -376,7 +376,7 @@ public class PetApi {
     String[] localVarAuthNames = new String[] { "api_key" };
 
     GenericType<Pet> localVarReturnType = new GenericType<Pet>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("PetApi.getPetById", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Update an existing pet
@@ -445,7 +445,7 @@ public class PetApi {
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     
-    return apiClient.invokeAPI(localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("PetApi.updatePet", localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Updates a pet in the store with form data
@@ -517,7 +517,7 @@ if (status != null)
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("PetApi.updatePetWithForm", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * uploads an image
@@ -590,7 +590,7 @@ if (file != null)
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     GenericType<ModelApiResponse> localVarReturnType = new GenericType<ModelApiResponse>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("PetApi.uploadFile", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * uploads an image (required)
@@ -668,6 +668,6 @@ if (requiredFile != null)
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     GenericType<ModelApiResponse> localVarReturnType = new GenericType<ModelApiResponse>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("PetApi.uploadFileWithRequiredFile", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
 }

samples/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/api/StoreApi.java

@@ -98,7 +98,7 @@ public class StoreApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("StoreApi.deleteOrder", localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Returns pet inventories by status
@@ -155,7 +155,7 @@ public class StoreApi {
     String[] localVarAuthNames = new String[] { "api_key" };
 
     GenericType<Map<String, Integer>> localVarReturnType = new GenericType<Map<String, Integer>>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("StoreApi.getInventory", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Find purchase order by ID
@@ -224,7 +224,7 @@ public class StoreApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<Order> localVarReturnType = new GenericType<Order>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("StoreApi.getOrderById", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Place an order for a pet
@@ -290,6 +290,6 @@ public class StoreApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<Order> localVarReturnType = new GenericType<Order>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("StoreApi.placeOrder", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
 }

samples/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/api/UserApi.java

@@ -95,7 +95,7 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("UserApi.createUser", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Creates list of users with given input array
@@ -158,7 +158,7 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("UserApi.createUsersWithArrayInput", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Creates list of users with given input array
@@ -221,7 +221,7 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("UserApi.createUsersWithListInput", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Delete user
@@ -287,7 +287,7 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("UserApi.deleteUser", localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Get user by user name
@@ -356,7 +356,7 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<User> localVarReturnType = new GenericType<User>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("UserApi.getUserByName", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Logs user into the system
@@ -431,7 +431,7 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<String> localVarReturnType = new GenericType<String>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("UserApi.loginUser", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Logs out current logged in user session
@@ -487,7 +487,7 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("UserApi.logoutUser", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Updated user
@@ -560,6 +560,6 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("UserApi.updateUser", localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
 }

samples/client/petstore/java/jersey2/src/main/java/org/openapitools/client/ApiClient.java

@@ -31,7 +31,9 @@ import java.util.Collections;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Arrays;
 import java.util.ArrayList;
 import java.util.Date;
 import java.util.TimeZone;
@@ -49,6 +51,7 @@ import org.openapitools.client.auth.Authentication;
 import org.openapitools.client.auth.HttpBasicAuth;
 import org.openapitools.client.auth.HttpBearerAuth;
 import org.openapitools.client.auth.ApiKeyAuth;
+
 import org.openapitools.client.auth.OAuth;
 
 
@@ -56,6 +59,19 @@ public class ApiClient {
   protected Map<String, String> defaultHeaderMap = new HashMap<String, String>();
   protected Map<String, String> defaultCookieMap = new HashMap<String, String>();
   protected String basePath = "http://petstore.swagger.io:80/v2";
+  protected List<ServerConfiguration> servers = new ArrayList<ServerConfiguration>(Arrays.asList(
+    new ServerConfiguration(
+      "http://petstore.swagger.io:80/v2",
+      "No description provided",
+      new HashMap<String, ServerVariable>()
+    )
+  ));
+  protected Integer serverIndex = 0;
+  protected Map<String, String> serverVariables = null;
+  protected Map<String, List<ServerConfiguration>> operationServers = new HashMap<String, List<ServerConfiguration>>() {{
+  }};
+  protected Map<String, Integer> operationServerIndex = new HashMap<String, Integer>();
+  protected Map<String, Map<String, String>> operationServerVariables = new HashMap<String, Map<String, String>>();
   protected boolean debugging = false;
   protected int connectionTimeout = 0;
   private int readTimeout = 0;
@@ -113,6 +129,33 @@ public class ApiClient {
     return this;
   }
 
+  public List<ServerConfiguration> getServers() {
+    return servers;
+  }
+
+  public ApiClient setServers(List<ServerConfiguration> servers) {
+    this.servers = servers;
+    return this;
+  }
+
+  public Integer getServerIndex() {
+    return serverIndex;
+  }
+
+  public ApiClient setServerIndex(Integer serverIndex) {
+    this.serverIndex = serverIndex;
+    return this;
+  }
+
+  public Map<String, String> getServerVariables() {
+    return serverVariables;
+  }
+
+  public ApiClient setServerVariables(Map<String, String> serverVariables) {
+    this.serverVariables = serverVariables;
+    return this;
+  }
+
   /**
    * Get authentications (key: authentication name, value: authentication).
    * @return Map of authentication object
@@ -654,6 +697,7 @@ public class ApiClient {
    * Invoke API by sending HTTP request with the given options.
    *
    * @param <T> Type
+   * @param operation The qualified name of the operation
    * @param path The sub-path of the HTTP URL
    * @param method The request method, one of "GET", "POST", "PUT", "HEAD" and "DELETE"
    * @param queryParams The query parameters
@@ -668,12 +712,36 @@ public class ApiClient {
    * @return The response body in type of string
    * @throws ApiException API exception
    */
-  public <T> ApiResponse<T> invokeAPI(String path, String method, List<Pair> queryParams, Object body, Map<String, String> headerParams, Map<String, String> cookieParams, Map<String, Object> formParams, String accept, String contentType, String[] authNames, GenericType<T> returnType) throws ApiException {
+  public <T> ApiResponse<T> invokeAPI(String operation, String path, String method, List<Pair> queryParams, Object body, Map<String, String> headerParams, Map<String, String> cookieParams, Map<String, Object> formParams, String accept, String contentType, String[] authNames, GenericType<T> returnType) throws ApiException {
     updateParamsForAuth(authNames, queryParams, headerParams, cookieParams);
 
-    // Not using `.target(this.basePath).path(path)` below,
+    // Not using `.target(targetURL).path(path)` below,
     // to support (constant) query string in `path`, e.g. "/posts?draft=1"
-    WebTarget target = httpClient.target(this.basePath + path);
+    String targetURL;
+    if (serverIndex != null) {
+      Integer index;
+      List<ServerConfiguration> serverConfigurations;
+      Map<String, String> variables;
+
+      if (operationServers.containsKey(operation)) {
+        index = operationServerIndex.getOrDefault(operation, serverIndex);
+        variables = operationServerVariables.getOrDefault(operation, serverVariables);
+        serverConfigurations = operationServers.get(operation);
+      } else {
+        index = serverIndex;
+        variables = serverVariables;
+        serverConfigurations = servers;
+      }
+      if (index < 0 || index >= serverConfigurations.size()) {
+        throw new ArrayIndexOutOfBoundsException(String.format(
+          "Invalid index %d when selecting the host settings. Must be less than %d", index, serverConfigurations.size()
+        ));
+      }
+      targetURL = serverConfigurations.get(index).URL(variables) + path;
+    } else {
+      targetURL = this.basePath + path;
+    }
+    WebTarget target = httpClient.target(targetURL);
 
     if (queryParams != null) {
       for (Pair queryParam : queryParams) {
@@ -777,6 +845,14 @@ public class ApiClient {
     }
   }
 
+  /**
+   * @deprecated Add qualified name of the operation as a first parameter.
+   */
+  @Deprecated
+  public <T> ApiResponse<T> invokeAPI(String path, String method, List<Pair> queryParams, Object body, Map<String, String> headerParams, Map<String, String> cookieParams, Map<String, Object> formParams, String accept, String contentType, String[] authNames, GenericType<T> returnType) throws ApiException {
+    return invokeAPI(null, path, method, queryParams, body, headerParams, cookieParams, formParams, accept, contentType, authNames, returnType);
+  }
+
   /**
    * Build the Client used to make HTTP requests.
    * @param debugging Debug setting

samples/client/petstore/java/jersey2/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/jersey2/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/jersey2/src/main/java/org/openapitools/client/api/AnotherFakeApi.java

@@ -96,6 +96,6 @@ public class AnotherFakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<Client> localVarReturnType = new GenericType<Client>() {};
-    return apiClient.invokeAPI(localVarPath, "PATCH", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("AnotherFakeApi.call123testSpecialTags", localVarPath, "PATCH", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
 }

samples/client/petstore/java/jersey2/src/main/java/org/openapitools/client/api/FakeApi.java

@@ -103,7 +103,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.createXmlItem", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * 
@@ -162,7 +162,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<Boolean> localVarReturnType = new GenericType<Boolean>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("FakeApi.fakeOuterBooleanSerialize", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * 
@@ -221,7 +221,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<OuterComposite> localVarReturnType = new GenericType<OuterComposite>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("FakeApi.fakeOuterCompositeSerialize", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * 
@@ -280,7 +280,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<BigDecimal> localVarReturnType = new GenericType<BigDecimal>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("FakeApi.fakeOuterNumberSerialize", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * 
@@ -339,7 +339,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<String> localVarReturnType = new GenericType<String>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("FakeApi.fakeOuterStringSerialize", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * 
@@ -402,7 +402,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testBodyWithFileSchema", localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * 
@@ -473,7 +473,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testBodyWithQueryParams", localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * To test \&quot;client\&quot; model
@@ -537,7 +537,7 @@ public class FakeApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<Client> localVarReturnType = new GenericType<Client>() {};
-    return apiClient.invokeAPI(localVarPath, "PATCH", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("FakeApi.testClientModel", localVarPath, "PATCH", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Fake endpoint for testing various parameters  假端點  偽のエンドポイント  가짜 엔드 포인트
@@ -671,7 +671,7 @@ if (paramCallback != null)
     String[] localVarAuthNames = new String[] { "http_basic_test" };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testEndpointParameters", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * To test enum parameters
@@ -757,7 +757,7 @@ if (enumFormString != null)
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testEnumParameters", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
 
 private ApiResponse<Void> testGroupParametersWithHttpInfo(Integer requiredStringGroup, Boolean requiredBooleanGroup, Long requiredInt64Group, Integer stringGroup, Boolean booleanGroup, Long int64Group) throws ApiException {
@@ -812,7 +812,7 @@ if (booleanGroup != null)
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testGroupParameters", localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
 
   public class APItestGroupParametersRequest {
@@ -999,7 +999,7 @@ if (booleanGroup != null)
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testInlineAdditionalProperties", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * test json serialization of form data
@@ -1073,7 +1073,7 @@ if (param2 != null)
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testJsonFormData", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * 
@@ -1169,6 +1169,6 @@ if (param2 != null)
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("FakeApi.testQueryParameterCollectionFormat", localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
 }

samples/client/petstore/java/jersey2/src/main/java/org/openapitools/client/api/FakeClassnameTags123Api.java

@@ -96,6 +96,6 @@ public class FakeClassnameTags123Api {
     String[] localVarAuthNames = new String[] { "api_key_query" };
 
     GenericType<Client> localVarReturnType = new GenericType<Client>() {};
-    return apiClient.invokeAPI(localVarPath, "PATCH", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("FakeClassnameTags123Api.testClassname", localVarPath, "PATCH", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
 }

samples/client/petstore/java/jersey2/src/main/java/org/openapitools/client/api/PetApi.java

@@ -99,7 +99,7 @@ public class PetApi {
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("PetApi.addPet", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Deletes a pet
@@ -169,7 +169,7 @@ public class PetApi {
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     
-    return apiClient.invokeAPI(localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("PetApi.deletePet", localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Finds Pets by status
@@ -236,7 +236,7 @@ public class PetApi {
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     GenericType<List<Pet>> localVarReturnType = new GenericType<List<Pet>>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("PetApi.findPetsByStatus", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Finds Pets by tags
@@ -307,7 +307,7 @@ public class PetApi {
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     GenericType<List<Pet>> localVarReturnType = new GenericType<List<Pet>>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("PetApi.findPetsByTags", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Find pet by ID
@@ -376,7 +376,7 @@ public class PetApi {
     String[] localVarAuthNames = new String[] { "api_key" };
 
     GenericType<Pet> localVarReturnType = new GenericType<Pet>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("PetApi.getPetById", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Update an existing pet
@@ -445,7 +445,7 @@ public class PetApi {
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     
-    return apiClient.invokeAPI(localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("PetApi.updatePet", localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Updates a pet in the store with form data
@@ -517,7 +517,7 @@ if (status != null)
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("PetApi.updatePetWithForm", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * uploads an image
@@ -590,7 +590,7 @@ if (file != null)
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     GenericType<ModelApiResponse> localVarReturnType = new GenericType<ModelApiResponse>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("PetApi.uploadFile", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * uploads an image (required)
@@ -668,6 +668,6 @@ if (requiredFile != null)
     String[] localVarAuthNames = new String[] { "petstore_auth" };
 
     GenericType<ModelApiResponse> localVarReturnType = new GenericType<ModelApiResponse>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("PetApi.uploadFileWithRequiredFile", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
 }

samples/client/petstore/java/jersey2/src/main/java/org/openapitools/client/api/StoreApi.java

@@ -98,7 +98,7 @@ public class StoreApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("StoreApi.deleteOrder", localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Returns pet inventories by status
@@ -155,7 +155,7 @@ public class StoreApi {
     String[] localVarAuthNames = new String[] { "api_key" };
 
     GenericType<Map<String, Integer>> localVarReturnType = new GenericType<Map<String, Integer>>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("StoreApi.getInventory", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Find purchase order by ID
@@ -224,7 +224,7 @@ public class StoreApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<Order> localVarReturnType = new GenericType<Order>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("StoreApi.getOrderById", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Place an order for a pet
@@ -290,6 +290,6 @@ public class StoreApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<Order> localVarReturnType = new GenericType<Order>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("StoreApi.placeOrder", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
 }

samples/client/petstore/java/jersey2/src/main/java/org/openapitools/client/api/UserApi.java

@@ -95,7 +95,7 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("UserApi.createUser", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Creates list of users with given input array
@@ -158,7 +158,7 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("UserApi.createUsersWithArrayInput", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Creates list of users with given input array
@@ -221,7 +221,7 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("UserApi.createUsersWithListInput", localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Delete user
@@ -287,7 +287,7 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("UserApi.deleteUser", localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Get user by user name
@@ -356,7 +356,7 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<User> localVarReturnType = new GenericType<User>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("UserApi.getUserByName", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Logs user into the system
@@ -431,7 +431,7 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     GenericType<String> localVarReturnType = new GenericType<String>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI("UserApi.loginUser", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
   }
   /**
    * Logs out current logged in user session
@@ -487,7 +487,7 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("UserApi.logoutUser", localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
   /**
    * Updated user
@@ -560,6 +560,6 @@ public class UserApi {
     String[] localVarAuthNames = new String[] {  };
 
     
-    return apiClient.invokeAPI(localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    return apiClient.invokeAPI("UserApi.updateUser", localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
   }
 }

samples/client/petstore/java/native/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/native/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/rest-assured/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/rest-assured/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/resteasy/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/resteasy/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/resttemplate/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/resttemplate/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/retrofit/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/retrofit/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/retrofit2-play24/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/retrofit2-play24/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/retrofit2-play25/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/retrofit2-play25/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/retrofit2-play26/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/retrofit2-play26/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/retrofit2/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/retrofit2/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/retrofit2rx/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/retrofit2rx/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/retrofit2rx2/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/retrofit2rx2/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/vertx/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/vertx/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/webclient/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/webclient/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}