Allows for generation of spring controller code using the delegate pattern (#4439)

* Allows for generation of spring conroller code using the decorator pattern

* Change Decorator to Delegate in spring codegen

modules/swagger-codegen/src/main/resources/JavaSpring/apiController.mustache

@@ -1,6 +1,6 @@
 package {{package}};
 
-{{^jdk8}}
+{{^jdk8-no-delegate}}
 {{#imports}}import {{import}};
 {{/imports}}
 
@@ -8,9 +8,9 @@ import io.swagger.annotations.*;
 
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
-{{/jdk8}}
+{{/jdk8-no-delegate}}
 import org.springframework.stereotype.Controller;
-{{^jdk8}}
+{{^jdk8-no-delegate}}
 import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RequestHeader;
@@ -21,24 +21,33 @@ import org.springframework.web.multipart.MultipartFile;
 import java.util.List;
 {{#async}}
 import java.util.concurrent.Callable;
-{{/async}}{{/jdk8}}
+{{/async}}{{/jdk8-no-delegate}}
 
 {{>generatedAnnotation}}
 @Controller
 {{#operations}}
 public class {{classname}}Controller implements {{classname}} {
-{{^jdk8}}{{#operation}}
+{{#isDelegate}}
+    private final {{classname}}Delegate delegate;
+
+    @org.springframework.beans.factory.annotation.Autowired
+    {{classname}}Controller({{classname}}Delegate delegate) {
+        this.delegate = delegate;
+    }{{/isDelegate}}
+
+{{^jdk8-no-delegate}}{{#operation}}
     public {{#async}}Callable<{{/async}}ResponseEntity<{{>returnTypes}}>{{#async}}>{{/async}} {{operationId}}({{#allParams}}{{>queryParams}}{{>pathParams}}{{>headerParams}}{{>bodyParams}}{{>formParams}}{{#hasMore}},
         {{/hasMore}}{{/allParams}}) {
-        // do some magic!{{^async}}
+        // do some magic!{{^isDelegate}}{{^async}}
         return new ResponseEntity<{{>returnTypes}}>(HttpStatus.OK);{{/async}}{{#async}}
         return new Callable<ResponseEntity<{{>returnTypes}}>>() {
             @Override
             public ResponseEntity<{{>returnTypes}}> call() throws Exception {
                 return new ResponseEntity<{{>returnTypes}}>(HttpStatus.OK);
             }
-        };{{/async}}
+        };{{/async}}{{/isDelegate}}{{#isDelegate}}
+        return delegate.{{operationId}}({{#allParams}}{{paramName}}{{#hasMore}}, {{/hasMore}}{{/allParams}});{{/isDelegate}}
     }
-{{/operation}}{{/jdk8}}
+{{/operation}}{{/jdk8-no-delegate}}
 }
 {{/operations}}

modules/swagger-codegen/src/main/resources/JavaSpring/apiDelegate.mustache

@@ -0,0 +1,37 @@
+package {{package}};
+
+{{#imports}}import {{import}};
+{{/imports}}
+
+import io.swagger.annotations.*;{{#jdk8}}
+import org.springframework.http.HttpStatus;{{/jdk8}}
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.multipart.MultipartFile;
+
+import java.util.List;
+{{#async}}
+import java.util.concurrent.{{^jdk8}}Callable{{/jdk8}}{{#jdk8}}CompletableFuture{{/jdk8}};
+{{/async}}
+
+{{#operations}}
+/**
+ * A delegate to be called by the {@link {{classname}}Controller}}.
+ * Should be implemented as a controller but without the {@link org.springframework.stereotype.Controller} annotation.
+ * Instead, use spring to autowire this class into the {@link {{classname}}Controller}.
+ */
+{{>generatedAnnotation}}
+public interface {{classname}}Delegate {
+
+{{#operation}}
+    /**
+     * @see {{classname}}#{{operationId}}
+     */
+    {{#jdk8}}default {{/jdk8}}{{#responseWrapper}}{{.}}<{{/responseWrapper}}ResponseEntity<{{>returnTypes}}>{{#responseWrapper}}>{{/responseWrapper}} {{operationId}}({{#allParams}}{{^isFile}}{{{dataType}}}{{/isFile}}{{#isFile}}MultipartFile{{/isFile}} {{paramName}}{{#hasMore}},
+        {{/hasMore}}{{/allParams}}){{^jdk8}};{{/jdk8}}{{#jdk8}} {
+    // do some magic!
+    return {{#async}}CompletableFuture.completedFuture({{/async}}new ResponseEntity<{{>returnTypes}}>(HttpStatus.OK){{#async}}){{/async}};
+    }{{/jdk8}}
+
+{{/operation}}
+}
+{{/operations}}