[Java] Fix for issue #3638: Generated Java APIs incorrectly encode commas in certain query parameters (#4908)

* Fix for issue #3638 * Update tests for fix for issue #3638 * Fix bug when queryParams and collectionQueryParams are both specified * Update tests * Add certain tests back, address CI failures
2017-06-14 12:20:04 -04:00
parent 1a421112ed
commit d20f83e643
22 changed files with 557 additions and 275 deletions
--- a/samples/client/petstore/java/jersey1/src/main/java/io/swagger/client/ApiClient.java
+++ b/samples/client/petstore/java/jersey1/src/main/java/io/swagger/client/ApiClient.java
@@ -400,62 +400,71 @@ public class ApiClient {
    }
  }

-  /*
-   * Format to {@code Pair} objects.
-   * @param collectionFormat Collection format
-   * @param name Name
-   * @param value Value
-   * @return List of pair
+  /**
+   * Formats the specified query parameter to a list containing a single {@code Pair} object.
+   *
+   * Note that {@code value} must not be a collection.
+   *
+   * @param name The name of the parameter.
+   * @param value The value of the parameter.
+   * @return A list containing a single {@code Pair} object.
   */
-  public List<Pair> parameterToPairs(String collectionFormat, String name, Object value){
+  public List<Pair> parameterToPair(String name, Object value) {
    List<Pair> params = new ArrayList<Pair>();

    // preconditions
-    if (name == null || name.isEmpty() || value == null) return params;
+    if (name == null || name.isEmpty() || value == null || value instanceof Collection) return params;

-    Collection<?> valueCollection;
-    if (value instanceof Collection<?>) {
-      valueCollection = (Collection<?>) value;
-    } else {
-      params.add(new Pair(name, parameterToString(value)));
+    params.add(new Pair(name, parameterToString(value)));
+    return params;
+  }
+
+  /**
+   * Formats the specified collection query parameters to a list of {@code Pair} objects.
+   *
+   * Note that the values of each of the returned Pair objects are percent-encoded.
+   *
+   * @param collectionFormat The collection format of the parameter.
+   * @param name The name of the parameter.
+   * @param value The value of the parameter.
+   * @return A list of {@code Pair} objects.
+   */
+  public List<Pair> parameterToPairs(String collectionFormat, String name, Collection value) {
+    List<Pair> params = new ArrayList<Pair>();
+
+    // preconditions
+    if (name == null || name.isEmpty() || value == null) {
      return params;
    }

-    if (valueCollection.isEmpty()){
-      return params;
-    }
-
-    // get the collection format
-    String format = (collectionFormat == null || collectionFormat.isEmpty() ? "csv" : collectionFormat); // default: csv
-
    // create the params based on the collection format
-    if ("multi".equals(format)) {
-      for (Object item : valueCollection) {
-        params.add(new Pair(name, parameterToString(item)));
+    if ("multi".equals(collectionFormat)) {
+      for (Object item : value) {
+        params.add(new Pair(name, escapeString(parameterToString(item))));
      }
-
      return params;
    }

+    // collectionFormat is assumed to be "csv" by default
    String delimiter = ",";

-    if ("csv".equals(format)) {
-      delimiter = ",";
-    } else if ("ssv".equals(format)) {
-      delimiter = " ";
-    } else if ("tsv".equals(format)) {
-      delimiter = "\t";
-    } else if ("pipes".equals(format)) {
-      delimiter = "|";
+    // escape all delimiters except commas, which are URI reserved
+    // characters
+    if ("ssv".equals(collectionFormat)) {
+      delimiter = escapeString(" ");
+    } else if ("tsv".equals(collectionFormat)) {
+      delimiter = escapeString("\t");
+    } else if ("pipes".equals(collectionFormat)) {
+      delimiter = escapeString("|");
    }

    StringBuilder sb = new StringBuilder() ;
-    for (Object item : valueCollection) {
+    for (Object item : value) {
      sb.append(delimiter);
-      sb.append(parameterToString(item));
+      sb.append(escapeString(parameterToString(item)));
    }

-    params.add(new Pair(name, sb.substring(1)));
+    params.add(new Pair(name, sb.substring(delimiter.length())));

    return params;
  }
@@ -571,9 +580,10 @@ public class ApiClient {
   *
   * @param path The sub path
   * @param queryParams The query parameters
+   * @param collectionQueryParams The collection query parameters
   * @return The full URL
   */
-  private String buildUrl(String path, List<Pair> queryParams) {
+  private String buildUrl(String path, List<Pair> queryParams, List<Pair> collectionQueryParams) {
    final StringBuilder url = new StringBuilder();
    url.append(basePath).append(path);

@@ -594,17 +604,34 @@ public class ApiClient {
      }
    }

+    if (collectionQueryParams != null && !collectionQueryParams.isEmpty()) {
+      String prefix = url.toString().contains("?") ? "&" : "?";
+      for (Pair param : collectionQueryParams) {
+        if (param.getValue() != null) {
+          if (prefix != null) {
+            url.append(prefix);
+            prefix = null;
+          } else {
+            url.append("&");
+          }
+          String value = parameterToString(param.getValue());
+          // collection query parameter value already escaped as part of parameterToPairs
+          url.append(escapeString(param.getName())).append("=").append(value);
+        }
+      }
+    }
+
    return url.toString();
  }

-  private ClientResponse getAPIResponse(String path, String method, List<Pair> queryParams, Object body, Map<String, String> headerParams, Map<String, Object> formParams, String accept, String contentType, String[] authNames) throws ApiException {
+  private ClientResponse getAPIResponse(String path, String method, List<Pair> queryParams, List<Pair> collectionQueryParams, Object body, Map<String, String> headerParams, Map<String, Object> formParams, String accept, String contentType, String[] authNames) throws ApiException {
    if (body != null && !formParams.isEmpty()) {
      throw new ApiException(500, "Cannot have body and form params");
    }

    updateParamsForAuth(authNames, queryParams, headerParams);

-    final String url = buildUrl(path, queryParams);
+    final String url = buildUrl(path, queryParams, collectionQueryParams);
    Builder builder;
    if (accept == null) {
      builder = httpClient.resource(url).getRequestBuilder();
@@ -647,6 +674,7 @@ public class ApiClient {
   * @param path The sub-path of the HTTP URL
   * @param method The request method, one of "GET", "POST", "PUT", and "DELETE"
   * @param queryParams The query parameters
+   * @param collectionQueryParams The collection query parameters
   * @param body The request body object - if it is not binary, otherwise null
   * @param headerParams The header parameters
   * @param formParams The form parameters
@@ -657,9 +685,9 @@ public class ApiClient {
   * @return The response body in type of string
   * @throws ApiException API exception
   */
-   public <T> T invokeAPI(String path, String method, List<Pair> queryParams, Object body, Map<String, String> headerParams, Map<String, Object> formParams, String accept, String contentType, String[] authNames, GenericType<T> returnType) throws ApiException {
+   public <T> T invokeAPI(String path, String method, List<Pair> queryParams, List<Pair> collectionQueryParams, Object body, Map<String, String> headerParams, Map<String, Object> formParams, String accept, String contentType, String[] authNames, GenericType<T> returnType) throws ApiException {

-    ClientResponse response = getAPIResponse(path, method, queryParams, body, headerParams, formParams, accept, contentType, authNames);
+    ClientResponse response = getAPIResponse(path, method, queryParams, collectionQueryParams, body, headerParams, formParams, accept, contentType, authNames);

    statusCode = response.getStatusInfo().getStatusCode();
    responseHeaders = response.getHeaders();
--- a/samples/client/petstore/java/jersey1/src/main/java/io/swagger/client/api/FakeApi.java
+++ b/samples/client/petstore/java/jersey1/src/main/java/io/swagger/client/api/FakeApi.java
@@ -67,6 +67,7 @@ public class FakeApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -86,7 +87,7 @@ public class FakeApi {
    String[] localVarAuthNames = new String[] {  };

    GenericType<Boolean> localVarReturnType = new GenericType<Boolean>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
      }
  /**
   * 
@@ -103,6 +104,7 @@ public class FakeApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -122,7 +124,7 @@ public class FakeApi {
    String[] localVarAuthNames = new String[] {  };

    GenericType<OuterComposite> localVarReturnType = new GenericType<OuterComposite>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
      }
  /**
   * 
@@ -139,6 +141,7 @@ public class FakeApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -158,7 +161,7 @@ public class FakeApi {
    String[] localVarAuthNames = new String[] {  };

    GenericType<BigDecimal> localVarReturnType = new GenericType<BigDecimal>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
      }
  /**
   * 
@@ -175,6 +178,7 @@ public class FakeApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -194,7 +198,7 @@ public class FakeApi {
    String[] localVarAuthNames = new String[] {  };

    GenericType<String> localVarReturnType = new GenericType<String>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
      }
  /**
   * To test \&quot;client\&quot; model
@@ -216,6 +220,7 @@ public class FakeApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -235,7 +240,7 @@ public class FakeApi {
    String[] localVarAuthNames = new String[] {  };

    GenericType<Client> localVarReturnType = new GenericType<Client>() {};
-    return apiClient.invokeAPI(localVarPath, "PATCH", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI(localVarPath, "PATCH", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, 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 
@@ -284,6 +289,7 @@ public class FakeApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -331,7 +337,7 @@ if (paramCallback != null)
    String[] localVarAuthNames = new String[] { "http_basic_test" };


-    apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
  }
  /**
   * To test enum parameters
@@ -354,12 +360,13 @@ if (paramCallback != null)

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

-    localVarQueryParams.addAll(apiClient.parameterToPairs("csv", "enum_query_string_array", enumQueryStringArray));
-    localVarQueryParams.addAll(apiClient.parameterToPairs("", "enum_query_string", enumQueryString));
-    localVarQueryParams.addAll(apiClient.parameterToPairs("", "enum_query_integer", enumQueryInteger));
+    localVarCollectionQueryParams.addAll(apiClient.parameterToPairs("csv", "enum_query_string_array", enumQueryStringArray));
+    localVarQueryParams.addAll(apiClient.parameterToPair("enum_query_string", enumQueryString));
+    localVarQueryParams.addAll(apiClient.parameterToPair("enum_query_integer", enumQueryInteger));

    if (enumHeaderStringArray != null)
      localVarHeaderParams.put("enum_header_string_array", apiClient.parameterToString(enumHeaderStringArray));
@@ -386,7 +393,7 @@ if (enumQueryDouble != null)
    String[] localVarAuthNames = new String[] {  };


-    apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
  }
  /**
   * test json serialization of form data
--- a/samples/client/petstore/java/jersey1/src/main/java/io/swagger/client/api/FakeClassnameTags123Api.java
+++ b/samples/client/petstore/java/jersey1/src/main/java/io/swagger/client/api/FakeClassnameTags123Api.java
@@ -68,6 +68,7 @@ public class FakeClassnameTags123Api {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -87,6 +88,6 @@ public class FakeClassnameTags123Api {
    String[] localVarAuthNames = new String[] {  };

    GenericType<Client> localVarReturnType = new GenericType<Client>() {};
-    return apiClient.invokeAPI(localVarPath, "PATCH", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI(localVarPath, "PATCH", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
      }
 }
--- a/samples/client/petstore/java/jersey1/src/main/java/io/swagger/client/api/PetApi.java
+++ b/samples/client/petstore/java/jersey1/src/main/java/io/swagger/client/api/PetApi.java
@@ -69,6 +69,7 @@ public class PetApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -88,7 +89,7 @@ public class PetApi {
    String[] localVarAuthNames = new String[] { "petstore_auth" };


-    apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
  }
  /**
   * Deletes a pet
@@ -111,6 +112,7 @@ public class PetApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -132,7 +134,7 @@ public class PetApi {
    String[] localVarAuthNames = new String[] { "petstore_auth" };


-    apiClient.invokeAPI(localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    apiClient.invokeAPI(localVarPath, "DELETE", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
  }
  /**
   * Finds Pets by status
@@ -154,10 +156,11 @@ public class PetApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

-    localVarQueryParams.addAll(apiClient.parameterToPairs("csv", "status", status));
+    localVarCollectionQueryParams.addAll(apiClient.parameterToPairs("csv", "status", status));

    
    
@@ -174,7 +177,7 @@ 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, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
      }
  /**
   * Finds Pets by tags
@@ -196,10 +199,11 @@ public class PetApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

-    localVarQueryParams.addAll(apiClient.parameterToPairs("csv", "tags", tags));
+    localVarCollectionQueryParams.addAll(apiClient.parameterToPairs("csv", "tags", tags));

    
    
@@ -216,7 +220,7 @@ 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, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
      }
  /**
   * Find pet by ID
@@ -239,6 +243,7 @@ public class PetApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -258,7 +263,7 @@ public class PetApi {
    String[] localVarAuthNames = new String[] { "api_key" };

    GenericType<Pet> localVarReturnType = new GenericType<Pet>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
      }
  /**
   * Update an existing pet
@@ -279,6 +284,7 @@ public class PetApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -298,7 +304,7 @@ public class PetApi {
    String[] localVarAuthNames = new String[] { "petstore_auth" };


-    apiClient.invokeAPI(localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    apiClient.invokeAPI(localVarPath, "PUT", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
  }
  /**
   * Updates a pet in the store with form data
@@ -322,6 +328,7 @@ public class PetApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -345,7 +352,7 @@ if (status != null)
    String[] localVarAuthNames = new String[] { "petstore_auth" };


-    apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
  }
  /**
   * uploads an image
@@ -370,6 +377,7 @@ if (status != null)

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -393,6 +401,6 @@ if (file != null)
    String[] localVarAuthNames = new String[] { "petstore_auth" };

    GenericType<ModelApiResponse> localVarReturnType = new GenericType<ModelApiResponse>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
      }
 }
--- a/samples/client/petstore/java/jersey1/src/main/java/io/swagger/client/api/StoreApi.java
+++ b/samples/client/petstore/java/jersey1/src/main/java/io/swagger/client/api/StoreApi.java
@@ -68,6 +68,7 @@ public class StoreApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -87,7 +88,7 @@ public class StoreApi {
    String[] localVarAuthNames = new String[] {  };


-    apiClient.invokeAPI(localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    apiClient.invokeAPI(localVarPath, "DELETE", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
  }
  /**
   * Returns pet inventories by status
@@ -103,6 +104,7 @@ public class StoreApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -122,7 +124,7 @@ 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, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
      }
  /**
   * Find purchase order by ID
@@ -145,6 +147,7 @@ public class StoreApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -164,7 +167,7 @@ public class StoreApi {
    String[] localVarAuthNames = new String[] {  };

    GenericType<Order> localVarReturnType = new GenericType<Order>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
      }
  /**
   * Place an order for a pet
@@ -186,6 +189,7 @@ public class StoreApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -205,6 +209,6 @@ public class StoreApi {
    String[] localVarAuthNames = new String[] {  };

    GenericType<Order> localVarReturnType = new GenericType<Order>() {};
-    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
      }
 }
--- a/samples/client/petstore/java/jersey1/src/main/java/io/swagger/client/api/UserApi.java
+++ b/samples/client/petstore/java/jersey1/src/main/java/io/swagger/client/api/UserApi.java
@@ -67,6 +67,7 @@ public class UserApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -86,7 +87,7 @@ public class UserApi {
    String[] localVarAuthNames = new String[] {  };


-    apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
  }
  /**
   * Creates list of users with given input array
@@ -107,6 +108,7 @@ public class UserApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -126,7 +128,7 @@ public class UserApi {
    String[] localVarAuthNames = new String[] {  };


-    apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
  }
  /**
   * Creates list of users with given input array
@@ -147,6 +149,7 @@ public class UserApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -166,7 +169,7 @@ public class UserApi {
    String[] localVarAuthNames = new String[] {  };


-    apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    apiClient.invokeAPI(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
  }
  /**
   * Delete user
@@ -188,6 +191,7 @@ public class UserApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -207,7 +211,7 @@ public class UserApi {
    String[] localVarAuthNames = new String[] {  };


-    apiClient.invokeAPI(localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    apiClient.invokeAPI(localVarPath, "DELETE", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
  }
  /**
   * Get user by user name
@@ -230,6 +234,7 @@ public class UserApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -249,7 +254,7 @@ public class UserApi {
    String[] localVarAuthNames = new String[] {  };

    GenericType<User> localVarReturnType = new GenericType<User>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
      }
  /**
   * Logs user into the system
@@ -277,11 +282,12 @@ public class UserApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

-    localVarQueryParams.addAll(apiClient.parameterToPairs("", "username", username));
-    localVarQueryParams.addAll(apiClient.parameterToPairs("", "password", password));
+    localVarQueryParams.addAll(apiClient.parameterToPair("username", username));
+    localVarQueryParams.addAll(apiClient.parameterToPair("password", password));

    
    
@@ -298,7 +304,7 @@ public class UserApi {
    String[] localVarAuthNames = new String[] {  };

    GenericType<String> localVarReturnType = new GenericType<String>() {};
-    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
+    return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType);
      }
  /**
   * Logs out current logged in user session
@@ -313,6 +319,7 @@ public class UserApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -332,7 +339,7 @@ public class UserApi {
    String[] localVarAuthNames = new String[] {  };


-    apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
  }
  /**
   * Updated user
@@ -360,6 +367,7 @@ public class UserApi {

    // query params
    List<Pair> localVarQueryParams = new ArrayList<Pair>();
+    List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
    Map<String, String> localVarHeaderParams = new HashMap<String, String>();
    Map<String, Object> localVarFormParams = new HashMap<String, Object>();

@@ -379,6 +387,6 @@ public class UserApi {
    String[] localVarAuthNames = new String[] {  };


-    apiClient.invokeAPI(localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
+    apiClient.invokeAPI(localVarPath, "PUT", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, null);
  }
 }
--- a/samples/client/petstore/java/jersey1/src/test/java/io/swagger/client/ApiClientTest.java
+++ b/samples/client/petstore/java/jersey1/src/test/java/io/swagger/client/ApiClientTest.java
@@ -167,10 +167,58 @@ public class ApiClientTest {
        auth.setApiKeyPrefix(null);
    }

+    @Test
+    public void testParameterToPairWhenNameIsInvalid() throws Exception {
+        List<Pair> pairs_a = apiClient.parameterToPair(null, new Integer(1));
+        List<Pair> pairs_b = apiClient.parameterToPair("", new Integer(1));
+
+        assertTrue(pairs_a.isEmpty());
+        assertTrue(pairs_b.isEmpty());
+    }
+
+    @Test
+    public void testParameterToPairWhenValueIsNull() throws Exception {
+        List<Pair> pairs = apiClient.parameterToPair("param-a", null);
+
+        assertTrue(pairs.isEmpty());
+    }
+
+    @Test
+    public void testParameterToPairWhenValueIsEmptyString() throws Exception {
+        // single empty string
+        List<Pair> pairs = apiClient.parameterToPair("param-a", " ");
+        assertEquals(1, pairs.size());
+    }
+
+    @Test
+    public void testParameterToPairWhenValueIsNotCollection() throws Exception {
+        String name = "param-a";
+        Integer value = 1;
+
+        List<Pair> pairs = apiClient.parameterToPair(name, value);
+
+        assertEquals(1, pairs.size());
+        assertEquals(value, Integer.valueOf(pairs.get(0).getValue()));
+    }
+
+    @Test
+    public void testParameterToPairWhenValueIsCollection() throws Exception {
+        List<Object> values = new ArrayList<Object>();
+        values.add("value-a");
+        values.add(123);
+        values.add(new Date());
+
+        List<Pair> pairs = apiClient.parameterToPair("param-a", values);
+        assertEquals(0, pairs.size());
+    }
+
    @Test
    public void testParameterToPairsWhenNameIsInvalid() throws Exception {
-        List<Pair> pairs_a = apiClient.parameterToPairs("csv", null, new Integer(1));
-        List<Pair> pairs_b = apiClient.parameterToPairs("csv", "", new Integer(1));
+        List<Integer> objects = new ArrayList<Integer>();
+        objects.add(new Integer(1));
+
+        List<Pair> pairs_a = apiClient.parameterToPairs("csv", null, objects);
+        List<Pair> pairs_b = apiClient.parameterToPairs("csv", "", objects);

        assertTrue(pairs_a.isEmpty());
        assertTrue(pairs_b.isEmpty());
@@ -185,11 +233,6 @@ public class ApiClientTest {

    @Test
    public void testParameterToPairsWhenValueIsEmptyStrings() throws Exception {
-
-        // single empty string
-        List<Pair> pairs = apiClient.parameterToPairs("csv", "param-a", " ");
-        assertEquals(1, pairs.size());
-
        // list of empty strings
        List<String> strs = new ArrayList<String>();
        strs.add(" ");
@@ -202,24 +245,13 @@ public class ApiClientTest {
        assertFalse(concatStrings.get(0).getValue().isEmpty()); // should contain some delimiters
    }

-    @Test
-    public void testParameterToPairsWhenValueIsNotCollection() throws Exception {
-        String name = "param-a";
-        Integer value = 1;
-
-        List<Pair> pairs = apiClient.parameterToPairs("csv", name, value);
-
-        assertEquals(1, pairs.size());
-        assertEquals(value, Integer.valueOf(pairs.get(0).getValue()));
-    }
-
    @Test
    public void testParameterToPairsWhenValueIsCollection() throws Exception {
        Map<String, String> collectionFormatMap = new HashMap<String, String>();
        collectionFormatMap.put("csv", ",");
        collectionFormatMap.put("tsv", "\t");
        collectionFormatMap.put("ssv", " ");
-        collectionFormatMap.put("pipes", "\\|");
+        collectionFormatMap.put("pipes", "|");
        collectionFormatMap.put("", ","); // no format, must default to csv
        collectionFormatMap.put("unknown", ","); // all other formats, must default to csv

@@ -233,6 +265,9 @@ public class ApiClientTest {
        // check for multi separately
        List<Pair> multiPairs = apiClient.parameterToPairs("multi", name, values);
        assertEquals(values.size(), multiPairs.size());
+        for (int i = 0; i < values.size(); i++) {
+            assertEquals(apiClient.escapeString(apiClient.parameterToString(values.get(i))), multiPairs.get(i).getValue());
+        }

        // all other formats
        for (String collectionFormat : collectionFormatMap.keySet()) {
@@ -241,10 +276,17 @@ public class ApiClientTest {
            assertEquals(1, pairs.size());

            String delimiter = collectionFormatMap.get(collectionFormat);
+            if (!delimiter.equals(",")) {
+                // commas are not escaped because they are reserved characters in URIs
+                delimiter = apiClient.escapeString(delimiter);
+            }
            String[] pairValueSplit = pairs.get(0).getValue().split(delimiter);

            // must equal input values
            assertEquals(values.size(), pairValueSplit.length);
+            for (int i = 0; i < values.size(); i++) {
+                assertEquals(apiClient.escapeString(apiClient.parameterToString(values.get(i))), pairValueSplit[i]);
+            }
        }
    }
 }
--- a/samples/client/petstore/java/okhttp-gson/docs/OuterBoolean.md
+++ b/samples/client/petstore/java/okhttp-gson/docs/OuterBoolean.md
@@ -0,0 +1,9 @@
+
+# OuterBoolean
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+
+
+
--- a/samples/client/petstore/java/okhttp-gson/docs/OuterNumber.md
+++ b/samples/client/petstore/java/okhttp-gson/docs/OuterNumber.md
@@ -0,0 +1,9 @@
+
+# OuterNumber
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+
+
+
--- a/samples/client/petstore/java/okhttp-gson/docs/OuterString.md
+++ b/samples/client/petstore/java/okhttp-gson/docs/OuterString.md
@@ -0,0 +1,9 @@
+
+# OuterString
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+
+
+
--- a/samples/client/petstore/java/okhttp-gson/src/main/java/io/swagger/client/ApiClient.java
+++ b/samples/client/petstore/java/okhttp-gson/src/main/java/io/swagger/client/ApiClient.java
@@ -466,62 +466,70 @@ public class ApiClient {
    }

    /**
-     * Format to {@code Pair} objects.
+     * Formats the specified query parameter to a list containing a single {@code Pair} object.
     *
-     * @param collectionFormat collection format (e.g. csv, tsv)
-     * @param name Name
-     * @param value Value
-     * @return A list of Pair objects
+     * Note that {@code value} must not be a collection.
+     *
+     * @param name The name of the parameter.
+     * @param value The value of the parameter.
+     * @return A list containing a single {@code Pair} object.
     */
-    public List<Pair> parameterToPairs(String collectionFormat, String name, Object value){
+    public List<Pair> parameterToPair(String name, Object value) {
        List<Pair> params = new ArrayList<Pair>();

        // preconditions
-        if (name == null || name.isEmpty() || value == null) return params;
+        if (name == null || name.isEmpty() || value == null || value instanceof Collection) return params;

-        Collection valueCollection = null;
-        if (value instanceof Collection) {
-            valueCollection = (Collection) value;
-        } else {
-            params.add(new Pair(name, parameterToString(value)));
+        params.add(new Pair(name, parameterToString(value)));
+        return params;
+    }
+
+    /**
+     * Formats the specified collection query parameters to a list of {@code Pair} objects.
+     *
+     * Note that the values of each of the returned Pair objects are percent-encoded.
+     *
+     * @param collectionFormat The collection format of the parameter.
+     * @param name The name of the parameter.
+     * @param value The value of the parameter.
+     * @return A list of {@code Pair} objects.
+     */
+    public List<Pair> parameterToPairs(String collectionFormat, String name, Collection value) {
+        List<Pair> params = new ArrayList<Pair>();
+
+        // preconditions
+        if (name == null || name.isEmpty() || value == null || value.isEmpty()) {
            return params;
        }

-        if (valueCollection.isEmpty()){
-            return params;
-        }
-
-        // get the collection format
-        collectionFormat = (collectionFormat == null || collectionFormat.isEmpty() ? "csv" : collectionFormat); // default: csv
-
        // create the params based on the collection format
-        if (collectionFormat.equals("multi")) {
-            for (Object item : valueCollection) {
-                params.add(new Pair(name, parameterToString(item)));
+        if ("multi".equals(collectionFormat)) {
+            for (Object item : value) {
+                params.add(new Pair(name, escapeString(parameterToString(item))));
            }
-
            return params;
        }

+        // collectionFormat is assumed to be "csv" by default
        String delimiter = ",";

-        if (collectionFormat.equals("csv")) {
-            delimiter = ",";
-        } else if (collectionFormat.equals("ssv")) {
-            delimiter = " ";
-        } else if (collectionFormat.equals("tsv")) {
-            delimiter = "\t";
-        } else if (collectionFormat.equals("pipes")) {
-            delimiter = "|";
+        // escape all delimiters except commas, which are URI reserved
+        // characters
+        if ("ssv".equals(collectionFormat)) {
+            delimiter = escapeString(" ");
+        } else if ("tsv".equals(collectionFormat)) {
+            delimiter = escapeString("\t");
+        } else if ("pipes".equals(collectionFormat)) {
+            delimiter = escapeString("|");
        }

        StringBuilder sb = new StringBuilder() ;
-        for (Object item : valueCollection) {
+        for (Object item : value) {
            sb.append(delimiter);
-            sb.append(parameterToString(item));
+            sb.append(escapeString(parameterToString(item)));
        }

-        params.add(new Pair(name, sb.substring(1)));
+        params.add(new Pair(name, sb.substring(delimiter.length())));

        return params;
    }
@@ -881,6 +889,7 @@ public class ApiClient {
     * @param path The sub-path of the HTTP URL
     * @param method The request method, one of "GET", "HEAD", "OPTIONS", "POST", "PUT", "PATCH" and "DELETE"
     * @param queryParams The query parameters
+     * @param collectionQueryParams The collection query parameters
     * @param body The request body object
     * @param headerParams The header parameters
     * @param formParams The form parameters
@@ -889,8 +898,8 @@ public class ApiClient {
     * @return The HTTP call
     * @throws ApiException If fail to serialize the request body object
     */
-    public Call buildCall(String path, String method, List<Pair> queryParams, Object body, Map<String, String> headerParams, Map<String, Object> formParams, String[] authNames, ProgressRequestBody.ProgressRequestListener progressRequestListener) throws ApiException {
-        Request request = buildRequest(path, method, queryParams, body, headerParams, formParams, authNames, progressRequestListener);
+    public Call buildCall(String path, String method, List<Pair> queryParams, List<Pair> collectionQueryParams, Object body, Map<String, String> headerParams, Map<String, Object> formParams, String[] authNames, ProgressRequestBody.ProgressRequestListener progressRequestListener) throws ApiException {
+        Request request = buildRequest(path, method, queryParams, collectionQueryParams, body, headerParams, formParams, authNames, progressRequestListener);

        return httpClient.newCall(request);
    }
@@ -901,6 +910,7 @@ public class ApiClient {
     * @param path The sub-path of the HTTP URL
     * @param method The request method, one of "GET", "HEAD", "OPTIONS", "POST", "PUT", "PATCH" and "DELETE"
     * @param queryParams The query parameters
+     * @param collectionQueryParams The collection query parameters
     * @param body The request body object
     * @param headerParams The header parameters
     * @param formParams The form parameters
@@ -909,10 +919,10 @@ public class ApiClient {
     * @return The HTTP request 
     * @throws ApiException If fail to serialize the request body object
     */
-    public Request buildRequest(String path, String method, List<Pair> queryParams, Object body, Map<String, String> headerParams, Map<String, Object> formParams, String[] authNames, ProgressRequestBody.ProgressRequestListener progressRequestListener) throws ApiException {
+    public Request buildRequest(String path, String method, List<Pair> queryParams, List<Pair> collectionQueryParams, Object body, Map<String, String> headerParams, Map<String, Object> formParams, String[] authNames, ProgressRequestBody.ProgressRequestListener progressRequestListener) throws ApiException {
        updateParamsForAuth(authNames, queryParams, headerParams);

-        final String url = buildUrl(path, queryParams);
+        final String url = buildUrl(path, queryParams, collectionQueryParams);
        final Request.Builder reqBuilder = new Request.Builder().url(url);
        processHeaderParams(headerParams, reqBuilder);

@@ -958,9 +968,10 @@ public class ApiClient {
     *
     * @param path The sub path
     * @param queryParams The query parameters
+     * @param collectionQueryParams The collection query parameters
     * @return The full URL
     */
-    public String buildUrl(String path, List<Pair> queryParams) {
+    public String buildUrl(String path, List<Pair> queryParams, List<Pair> collectionQueryParams) {
        final StringBuilder url = new StringBuilder();
        url.append(basePath).append(path);

@@ -981,6 +992,23 @@ public class ApiClient {
            }
        }

+        if (collectionQueryParams != null && !collectionQueryParams.isEmpty()) {
+            String prefix = url.toString().contains("?") ? "&" : "?";
+            for (Pair param : collectionQueryParams) {
+                if (param.getValue() != null) {
+                    if (prefix != null) {
+                        url.append(prefix);
+                        prefix = null;
+                    } else {
+                        url.append("&");
+                    }
+                    String value = parameterToString(param.getValue());
+                    // collection query parameter value already escaped as part of parameterToPairs
+                    url.append(escapeString(param.getName())).append("=").append(value);
+                }
+            }
+        }
+
        return url.toString();
    }

--- a/samples/client/petstore/java/okhttp-gson/src/main/java/io/swagger/client/api/FakeApi.java
+++ b/samples/client/petstore/java/okhttp-gson/src/main/java/io/swagger/client/api/FakeApi.java
@@ -73,6 +73,7 @@ public class FakeApi {
        String localVarPath = "/fake/outer/boolean";

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -103,7 +104,7 @@ public class FakeApi {
        }

        String[] localVarAuthNames = new String[] {  };
-        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -193,6 +194,7 @@ public class FakeApi {
        String localVarPath = "/fake/outer/composite";

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -223,7 +225,7 @@ public class FakeApi {
        }

        String[] localVarAuthNames = new String[] {  };
-        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -313,6 +315,7 @@ public class FakeApi {
        String localVarPath = "/fake/outer/number";

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -343,7 +346,7 @@ public class FakeApi {
        }

        String[] localVarAuthNames = new String[] {  };
-        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -433,6 +436,7 @@ public class FakeApi {
        String localVarPath = "/fake/outer/string";

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -463,7 +467,7 @@ public class FakeApi {
        }

        String[] localVarAuthNames = new String[] {  };
-        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -553,6 +557,7 @@ public class FakeApi {
        String localVarPath = "/fake";

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -583,7 +588,7 @@ public class FakeApi {
        }

        String[] localVarAuthNames = new String[] {  };
-        return apiClient.buildCall(localVarPath, "PATCH", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "PATCH", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -691,6 +696,7 @@ public class FakeApi {
        String localVarPath = "/fake";

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -749,7 +755,7 @@ public class FakeApi {
        }

        String[] localVarAuthNames = new String[] { "http_basic_test" };
-        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -901,12 +907,13 @@ public class FakeApi {
        String localVarPath = "/fake";

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
        if (enumQueryStringArray != null)
-        localVarQueryParams.addAll(apiClient.parameterToPairs("csv", "enum_query_string_array", enumQueryStringArray));
+        localVarCollectionQueryParams.addAll(apiClient.parameterToPairs("csv", "enum_query_string_array", enumQueryStringArray));
        if (enumQueryString != null)
-        localVarQueryParams.addAll(apiClient.parameterToPairs("", "enum_query_string", enumQueryString));
+        localVarQueryParams.addAll(apiClient.parameterToPair("enum_query_string", enumQueryString));
        if (enumQueryInteger != null)
-        localVarQueryParams.addAll(apiClient.parameterToPairs("", "enum_query_integer", enumQueryInteger));
+        localVarQueryParams.addAll(apiClient.parameterToPair("enum_query_integer", enumQueryInteger));

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();
        if (enumHeaderStringArray != null)
@@ -947,7 +954,7 @@ public class FakeApi {
        }

        String[] localVarAuthNames = new String[] {  };
-        return apiClient.buildCall(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "GET", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
--- a/samples/client/petstore/java/okhttp-gson/src/main/java/io/swagger/client/api/FakeClassnameTags123Api.java
+++ b/samples/client/petstore/java/okhttp-gson/src/main/java/io/swagger/client/api/FakeClassnameTags123Api.java
@@ -69,6 +69,7 @@ public class FakeClassnameTags123Api {
        String localVarPath = "/fake_classname_test";

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -99,7 +100,7 @@ public class FakeClassnameTags123Api {
        }

        String[] localVarAuthNames = new String[] {  };
-        return apiClient.buildCall(localVarPath, "PATCH", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "PATCH", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
--- a/samples/client/petstore/java/okhttp-gson/src/main/java/io/swagger/client/api/PetApi.java
+++ b/samples/client/petstore/java/okhttp-gson/src/main/java/io/swagger/client/api/PetApi.java
@@ -71,6 +71,7 @@ public class PetApi {
        String localVarPath = "/pet";

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -101,7 +102,7 @@ public class PetApi {
        }

        String[] localVarAuthNames = new String[] { "petstore_auth" };
-        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -194,6 +195,7 @@ public class PetApi {
            .replaceAll("\\{" + "petId" + "\\}", apiClient.escapeString(petId.toString()));

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();
        if (apiKey != null)
@@ -226,7 +228,7 @@ public class PetApi {
        }

        String[] localVarAuthNames = new String[] { "petstore_auth" };
-        return apiClient.buildCall(localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "DELETE", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -320,8 +322,9 @@ public class PetApi {
        String localVarPath = "/pet/findByStatus";

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
        if (status != null)
-        localVarQueryParams.addAll(apiClient.parameterToPairs("csv", "status", status));
+        localVarCollectionQueryParams.addAll(apiClient.parameterToPairs("csv", "status", status));

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -352,7 +355,7 @@ public class PetApi {
        }

        String[] localVarAuthNames = new String[] { "petstore_auth" };
-        return apiClient.buildCall(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "GET", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -447,8 +450,9 @@ public class PetApi {
        String localVarPath = "/pet/findByTags";

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
        if (tags != null)
-        localVarQueryParams.addAll(apiClient.parameterToPairs("csv", "tags", tags));
+        localVarCollectionQueryParams.addAll(apiClient.parameterToPairs("csv", "tags", tags));

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -479,7 +483,7 @@ public class PetApi {
        }

        String[] localVarAuthNames = new String[] { "petstore_auth" };
-        return apiClient.buildCall(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "GET", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -575,6 +579,7 @@ public class PetApi {
            .replaceAll("\\{" + "petId" + "\\}", apiClient.escapeString(petId.toString()));

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -605,7 +610,7 @@ public class PetApi {
        }

        String[] localVarAuthNames = new String[] { "api_key" };
-        return apiClient.buildCall(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "GET", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -700,6 +705,7 @@ public class PetApi {
        String localVarPath = "/pet";

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -730,7 +736,7 @@ public class PetApi {
        }

        String[] localVarAuthNames = new String[] { "petstore_auth" };
-        return apiClient.buildCall(localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "PUT", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -824,6 +830,7 @@ public class PetApi {
            .replaceAll("\\{" + "petId" + "\\}", apiClient.escapeString(petId.toString()));

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -858,7 +865,7 @@ public class PetApi {
        }

        String[] localVarAuthNames = new String[] { "petstore_auth" };
-        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -958,6 +965,7 @@ public class PetApi {
            .replaceAll("\\{" + "petId" + "\\}", apiClient.escapeString(petId.toString()));

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -992,7 +1000,7 @@ public class PetApi {
        }

        String[] localVarAuthNames = new String[] { "petstore_auth" };
-        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
--- a/samples/client/petstore/java/okhttp-gson/src/main/java/io/swagger/client/api/StoreApi.java
+++ b/samples/client/petstore/java/okhttp-gson/src/main/java/io/swagger/client/api/StoreApi.java
@@ -70,6 +70,7 @@ public class StoreApi {
            .replaceAll("\\{" + "order_id" + "\\}", apiClient.escapeString(orderId.toString()));

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -100,7 +101,7 @@ public class StoreApi {
        }

        String[] localVarAuthNames = new String[] {  };
-        return apiClient.buildCall(localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "DELETE", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -190,6 +191,7 @@ public class StoreApi {
        String localVarPath = "/store/inventory";

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -220,7 +222,7 @@ public class StoreApi {
        }

        String[] localVarAuthNames = new String[] { "api_key" };
-        return apiClient.buildCall(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "GET", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -308,6 +310,7 @@ public class StoreApi {
            .replaceAll("\\{" + "order_id" + "\\}", apiClient.escapeString(orderId.toString()));

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -338,7 +341,7 @@ public class StoreApi {
        }

        String[] localVarAuthNames = new String[] {  };
-        return apiClient.buildCall(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "GET", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -433,6 +436,7 @@ public class StoreApi {
        String localVarPath = "/store/order";

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -463,7 +467,7 @@ public class StoreApi {
        }

        String[] localVarAuthNames = new String[] {  };
-        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
--- a/samples/client/petstore/java/okhttp-gson/src/main/java/io/swagger/client/api/UserApi.java
+++ b/samples/client/petstore/java/okhttp-gson/src/main/java/io/swagger/client/api/UserApi.java
@@ -69,6 +69,7 @@ public class UserApi {
        String localVarPath = "/user";

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -99,7 +100,7 @@ public class UserApi {
        }

        String[] localVarAuthNames = new String[] {  };
-        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -190,6 +191,7 @@ public class UserApi {
        String localVarPath = "/user/createWithArray";

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -220,7 +222,7 @@ public class UserApi {
        }

        String[] localVarAuthNames = new String[] {  };
-        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -311,6 +313,7 @@ public class UserApi {
        String localVarPath = "/user/createWithList";

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -341,7 +344,7 @@ public class UserApi {
        }

        String[] localVarAuthNames = new String[] {  };
-        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "POST", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -433,6 +436,7 @@ public class UserApi {
            .replaceAll("\\{" + "username" + "\\}", apiClient.escapeString(username.toString()));

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -463,7 +467,7 @@ public class UserApi {
        }

        String[] localVarAuthNames = new String[] {  };
-        return apiClient.buildCall(localVarPath, "DELETE", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "DELETE", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -555,6 +559,7 @@ public class UserApi {
            .replaceAll("\\{" + "username" + "\\}", apiClient.escapeString(username.toString()));

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -585,7 +590,7 @@ public class UserApi {
        }

        String[] localVarAuthNames = new String[] {  };
-        return apiClient.buildCall(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "GET", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -681,10 +686,11 @@ public class UserApi {
        String localVarPath = "/user/login";

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
        if (username != null)
-        localVarQueryParams.addAll(apiClient.parameterToPairs("", "username", username));
+        localVarQueryParams.addAll(apiClient.parameterToPair("username", username));
        if (password != null)
-        localVarQueryParams.addAll(apiClient.parameterToPairs("", "password", password));
+        localVarQueryParams.addAll(apiClient.parameterToPair("password", password));

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -715,7 +721,7 @@ public class UserApi {
        }

        String[] localVarAuthNames = new String[] {  };
-        return apiClient.buildCall(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "GET", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -817,6 +823,7 @@ public class UserApi {
        String localVarPath = "/user/logout";

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -847,7 +854,7 @@ public class UserApi {
        }

        String[] localVarAuthNames = new String[] {  };
-        return apiClient.buildCall(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "GET", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
@@ -932,6 +939,7 @@ public class UserApi {
            .replaceAll("\\{" + "username" + "\\}", apiClient.escapeString(username.toString()));

        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();

        Map<String, String> localVarHeaderParams = new HashMap<String, String>();

@@ -962,7 +970,7 @@ public class UserApi {
        }

        String[] localVarAuthNames = new String[] {  };
-        return apiClient.buildCall(localVarPath, "PUT", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
+        return apiClient.buildCall(localVarPath, "PUT", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarFormParams, localVarAuthNames, progressRequestListener);
    }
    
    @SuppressWarnings("rawtypes")
--- a/samples/client/petstore/java/okhttp-gson/src/test/java/io/swagger/client/ApiClientTest.java
+++ b/samples/client/petstore/java/okhttp-gson/src/test/java/io/swagger/client/ApiClientTest.java
@@ -166,10 +166,58 @@ public class ApiClientTest {
        apiClient.setConnectTimeout(10000);
    }

+    @Test
+    public void testParameterToPairWhenNameIsInvalid() throws Exception {
+        List<Pair> pairs_a = apiClient.parameterToPair(null, new Integer(1));
+        List<Pair> pairs_b = apiClient.parameterToPair("", new Integer(1));
+
+        assertTrue(pairs_a.isEmpty());
+        assertTrue(pairs_b.isEmpty());
+    }
+
+    @Test
+    public void testParameterToPairWhenValueIsNull() throws Exception {
+        List<Pair> pairs = apiClient.parameterToPair("param-a", null);
+
+        assertTrue(pairs.isEmpty());
+    }
+
+    @Test
+    public void testParameterToPairWhenValueIsEmptyString() throws Exception {
+        // single empty string
+        List<Pair> pairs = apiClient.parameterToPair("param-a", " ");
+        assertEquals(1, pairs.size());
+    }
+
+    @Test
+    public void testParameterToPairWhenValueIsNotCollection() throws Exception {
+        String name = "param-a";
+        Integer value = 1;
+
+        List<Pair> pairs = apiClient.parameterToPair(name, value);
+
+        assertEquals(1, pairs.size());
+        assertEquals(value, Integer.valueOf(pairs.get(0).getValue()));
+    }
+
+    @Test
+    public void testParameterToPairWhenValueIsCollection() throws Exception {
+        List<Object> values = new ArrayList<Object>();
+        values.add("value-a");
+        values.add(123);
+        values.add(new Date());
+
+        List<Pair> pairs = apiClient.parameterToPair("param-a", values);
+        assertEquals(0, pairs.size());
+    }
+
    @Test
    public void testParameterToPairsWhenNameIsInvalid() throws Exception {
-        List<Pair> pairs_a = apiClient.parameterToPairs("csv", null, new Integer(1));
-        List<Pair> pairs_b = apiClient.parameterToPairs("csv", "", new Integer(1));
+        List<Integer> objects = new ArrayList<Integer>();
+        objects.add(new Integer(1));
+
+        List<Pair> pairs_a = apiClient.parameterToPairs("csv", null, objects);
+        List<Pair> pairs_b = apiClient.parameterToPairs("csv", "", objects);

        assertTrue(pairs_a.isEmpty());
        assertTrue(pairs_b.isEmpty());
@@ -184,11 +232,6 @@ public class ApiClientTest {

    @Test
    public void testParameterToPairsWhenValueIsEmptyStrings() throws Exception {
-
-        // single empty string
-        List<Pair> pairs = apiClient.parameterToPairs("csv", "param-a", " ");
-        assertEquals(1, pairs.size());
-
        // list of empty strings
        List<String> strs = new ArrayList<String>();
        strs.add(" ");
@@ -201,24 +244,13 @@ public class ApiClientTest {
        assertFalse(concatStrings.get(0).getValue().isEmpty()); // should contain some delimiters
    }

-    @Test
-    public void testParameterToPairsWhenValueIsNotCollection() throws Exception {
-        String name = "param-a";
-        Integer value = 1;
-
-        List<Pair> pairs = apiClient.parameterToPairs("csv", name, value);
-
-        assertEquals(1, pairs.size());
-        assertEquals(value, Integer.valueOf(pairs.get(0).getValue()));
-    }
-
    @Test
    public void testParameterToPairsWhenValueIsCollection() throws Exception {
        Map<String, String> collectionFormatMap = new HashMap<String, String>();
        collectionFormatMap.put("csv", ",");
        collectionFormatMap.put("tsv", "\t");
        collectionFormatMap.put("ssv", " ");
-        collectionFormatMap.put("pipes", "\\|");
+        collectionFormatMap.put("pipes", "|");
        collectionFormatMap.put("", ","); // no format, must default to csv
        collectionFormatMap.put("unknown", ","); // all other formats, must default to csv

@@ -232,6 +264,9 @@ public class ApiClientTest {
        // check for multi separately
        List<Pair> multiPairs = apiClient.parameterToPairs("multi", name, values);
        assertEquals(values.size(), multiPairs.size());
+        for (int i = 0; i < values.size(); i++) {
+            assertEquals(apiClient.escapeString(apiClient.parameterToString(values.get(i))), multiPairs.get(i).getValue());
+        }

        // all other formats
        for (String collectionFormat : collectionFormatMap.keySet()) {
@@ -240,10 +275,17 @@ public class ApiClientTest {
            assertEquals(1, pairs.size());

            String delimiter = collectionFormatMap.get(collectionFormat);
+            if (!delimiter.equals(",")) {
+                // commas are not escaped because they are reserved characters in URIs
+                delimiter = apiClient.escapeString(delimiter);
+            }
            String[] pairValueSplit = pairs.get(0).getValue().split(delimiter);

            // must equal input values
            assertEquals(values.size(), pairValueSplit.length);
+            for (int i = 0; i < values.size(); i++) {
+                assertEquals(apiClient.escapeString(apiClient.parameterToString(values.get(i))), pairValueSplit[i]);
+            }
        }
    }