Add support for using Spring HATEOAS to add links in the spring gener… (#1130)

* Add support for using Spring HATEOAS to add links in the spring generator.

* Ensure that Spring HATEOAS links appear last in the JSON serialisation of objects.

* A couple of changes following code review:
1. Make sure the @JsonPropertyOrder annotation is only used when the jackson library is being used since it's a part of the jackson library.
2. Make sure to include the Spring HATEOAS dependency in the pom file for the spring-cloud and spring-mvc generators when the hateoas option is enabled.

* Don't order the json properties since there's no requirement for the links to be last.

* Remove unnecessary import.

docs/generators/spring.md

@@ -164,6 +164,9 @@ CONFIG OPTIONS for spring
 	useOptional
 	    Use Optional container for optional parameters (Default: false)
 
+	hateoas
+	    Use Spring HATEOAS library to allow adding HATEOAS links (Default: false)
+
 	library
 	    library template (sub-template) to use (Default: spring-boot)
 	        spring-boot - Spring-boot Server application using the SpringFox integration.

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

@@ -74,6 +74,7 @@ public class SpringCodegen extends AbstractJavaCodegen
     public static final String IMPLICIT_HEADERS = "implicitHeaders";
     public static final String OPENAPI_DOCKET_CONFIG = "swaggerDocketConfig";
     public static final String API_FIRST = "apiFirst";
+    public static final String HATEOAS = "hateoas";
 
     protected String title = "OpenAPI Spring";
     protected String configPackage = "org.openapitools.configuration";
@@ -93,6 +94,7 @@ public class SpringCodegen extends AbstractJavaCodegen
     protected boolean apiFirst = false;
     protected boolean useOptional = false;
     protected boolean virtualService = false;
+    protected boolean hateoas = false;
 
     public SpringCodegen() {
         super();
@@ -124,6 +126,7 @@ public class SpringCodegen extends AbstractJavaCodegen
         cliOptions.add(CliOption.newBoolean(OPENAPI_DOCKET_CONFIG, "Generate Spring OpenAPI Docket configuration class.", openapiDocketConfig));
         cliOptions.add(CliOption.newBoolean(API_FIRST, "Generate the API from the OAI spec at server compile time (API first approach)", apiFirst));
         cliOptions.add(CliOption.newBoolean(USE_OPTIONAL,"Use Optional container for optional parameters", useOptional));
+        cliOptions.add(CliOption.newBoolean(HATEOAS, "Use Spring HATEOAS library to allow adding HATEOAS links", hateoas));
 
         supportedLibraries.put(SPRING_BOOT, "Spring-boot Server application using the SpringFox integration.");
         supportedLibraries.put(SPRING_MVC_LIBRARY, "Spring-MVC Server application using the SpringFox integration.");
@@ -260,6 +263,10 @@ public class SpringCodegen extends AbstractJavaCodegen
         if (additionalProperties.containsKey(API_FIRST)) {
             this.setApiFirst(Boolean.valueOf(additionalProperties.get(API_FIRST).toString()));
         }
+        
+        if (additionalProperties.containsKey(HATEOAS)) {
+            this.setHateoas(Boolean.valueOf(additionalProperties.get(HATEOAS).toString()));
+        }
 
         typeMapping.put("file", "Resource");
         importMapping.put("Resource", "org.springframework.core.io.Resource");
@@ -700,6 +707,10 @@ public class SpringCodegen extends AbstractJavaCodegen
     public void setApiFirst(boolean apiFirst) {
         this.apiFirst = apiFirst;
     }
+    
+    public void setHateoas(boolean hateoas) {
+        this.hateoas = hateoas;
+    }
 
     @Override
     public void postProcessModelProperty(CodegenModel model, CodegenProperty property) {

modules/openapi-generator/src/main/resources/JavaSpring/libraries/spring-boot/pom.mustache

@@ -164,5 +164,12 @@
         </dependency>
     <!-- END Virtual Service API support -->
 {{/virtualService}}
+{{#hateoas}}
+        <!-- Spring HATEOAS -->
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-hateoas</artifactId>
+        </dependency>
+{{/hateoas}}
     </dependencies>
 </project>

modules/openapi-generator/src/main/resources/JavaSpring/libraries/spring-cloud/pom.mustache

@@ -86,5 +86,12 @@
             <artifactId>spring-boot-starter-test</artifactId>
             <scope>test</scope>
         </dependency>
+{{#hateoas}}
+        <!-- Spring HATEOAS -->
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-hateoas</artifactId>
+        </dependency>
+{{/hateoas}}
     </dependencies>
 </project>

modules/openapi-generator/src/main/resources/JavaSpring/libraries/spring-mvc/pom.mustache

@@ -222,6 +222,14 @@
             <scope>provided</scope>
         </dependency>
 {{/useBeanValidation}}
+{{#hateoas}}
+        <!-- Spring HATEOAS -->
+        <dependency>
+            <groupId>org.springframework.hateoas</groupId>
+            <artifactId>spring-hateoas</artifactId>
+            <version>0.25.0.RELEASE</version>
+        </dependency>
+{{/hateoas}}
     </dependencies>
     <properties>
         <java.version>{{#java8}}1.8{{/java8}}{{^java8}}1.7{{/java8}}</java.version>

modules/openapi-generator/src/main/resources/JavaSpring/model.mustache

@@ -19,6 +19,11 @@ import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlProperty;
 {{#withXml}}
 import javax.xml.bind.annotation.*;
 {{/withXml}}
+{{^parent}}
+{{#hateoas}}
+import org.springframework.hateoas.ResourceSupport;
+{{/hateoas}}
+{{/parent}}
 
 {{#models}}
 {{#model}}

modules/openapi-generator/src/main/resources/JavaSpring/pojo.mustache

@@ -3,7 +3,7 @@
  */{{#description}}
 @ApiModel(description = "{{{description}}}"){{/description}}
 {{>generatedAnnotation}}{{#discriminator}}{{>typeInfoAnnotation}}{{/discriminator}}{{>xmlAnnotation}}
-public class {{classname}} {{#parent}}extends {{{parent}}}{{/parent}} {{#serializableModel}}implements Serializable{{/serializableModel}} {
+public class {{classname}} {{#parent}}extends {{{parent}}}{{/parent}}{{^parent}}{{#hateoas}}extends ResourceSupport {{/hateoas}}{{/parent}} {{#serializableModel}}implements Serializable{{/serializableModel}} {
 {{#serializableModel}}
   private static final long serialVersionUID = 1L;