Improved support for empty response definition and response schema ge…

modules/swagger-annotations/src/main/java/io/swagger/v3/oas/annotations/media/Schema.java

@@ -23,7 +23,6 @@
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
-import java.nio.file.AccessMode;
 
 import static java.lang.annotation.ElementType.ANNOTATION_TYPE;
 import static java.lang.annotation.ElementType.TYPE;
@@ -335,4 +334,14 @@ enum AccessMode {
         WRITE_ONLY,
         READ_WRITE;
     }
+
+    /**
+     * Marker class to use on the {@link Schema} implementation field to set that a
+     * response has no content.
+     * 
+     * @author Ariel Carrera
+     *
+     */
+    public static class Empty {
+    }
 }

modules/swagger-core/src/main/java/io/swagger/v3/core/util/AnnotationsUtils.java

@@ -13,6 +13,7 @@
 import io.swagger.v3.oas.annotations.links.LinkParameter;
 import io.swagger.v3.oas.annotations.media.DiscriminatorMapping;
 import io.swagger.v3.oas.annotations.media.ExampleObject;
+import io.swagger.v3.oas.annotations.media.Schema.Empty;
 import io.swagger.v3.oas.models.Components;
 import io.swagger.v3.oas.models.ExternalDocumentation;
 import io.swagger.v3.oas.models.examples.Example;
@@ -540,12 +541,17 @@ public static Optional<Schema> getSchemaFromAnnotation(io.swagger.v3.oas.annotat
             }
         }
 
-
+        if (schemaObject.isEmpty()) {
+            return Optional.of(schemaObject.noContent(true));
+        }
         return Optional.of(schemaObject);
     }
 
     public static Schema resolveSchemaFromType(Class<?> schemaImplementation, Components components, JsonView jsonViewAnnotation) {
-        Schema schemaObject;
+	if (Empty.class.equals(schemaImplementation)) {
+	    return new Schema().noContent(true);
+	}
+	Schema schemaObject;
         PrimitiveType primitiveType = PrimitiveType.fromType(schemaImplementation);
         if (primitiveType != null) {
             schemaObject = primitiveType.createProperty();
@@ -1088,6 +1094,8 @@ public static Optional<? extends Schema> getSchema(io.swagger.v3.oas.annotations
             if (schemaImplementation != Void.class) {
                 isArray = true;
             }
+        } else if (schemaImplementation == Empty.class) {
+            return Optional.of(new Schema<>().noContent(true));
         }
         return getSchema(annotationContent.schema(), annotationContent.array(), isArray, schemaImplementation, components, jsonViewAnnotation);
     }

modules/swagger-jaxrs2/src/main/java/io/swagger/v3/jaxrs2/Reader.java

@@ -1089,6 +1089,38 @@ protected Operation parseMethod(
                         }
                     }
                 }
+                operation.getResponses().forEach((k, value) -> {
+                    if (value.getContent() == null) { // no content annotation -> DEFAULT CONTENT/SCHEMA
+                        value.setContent(content);
+                    } else if (!"default".equals(k)) {
+                        Set<String> contentsToRemove = new HashSet<>();
+                        value.getContent().forEach((mediaStr, mediaObj) -> {
+                            if (mediaObj.isEmpty()) { // content annotation empty or only mediaType field defined -> DEFAULT CONTENT/SCHEMA
+                                if (value.getContent().size() == 1) {
+                                    value.setContent(new Content().addMediaType(mediaStr, mediaType));
+                                } else {
+                                    mediaObj.setSchema(returnTypeSchema);
+                                }
+                            } else {
+                                Schema schemaObj = mediaObj.getSchema();
+                                if (schemaObj == null || schemaObj.isEmpty()) {
+                                    mediaObj.setSchema(returnTypeSchema);
+                                } else if (schemaObj.isNoContent()) {
+                                    mediaObj.setSchema(null);
+                                    if (mediaObj.isEmpty()) {
+                                        contentsToRemove.add(mediaStr);
+                                    }
+                                }
+                            }
+                        });
+
+                        contentsToRemove.stream().forEach(s -> value.getContent().remove(s));
+                        if (value.getContent().isEmpty()) {
+                            value.setContent(null);
+                        }
+                    }
+                });
+
                 Map<String, Schema> schemaMap = resolvedSchema.referencedSchemas;
                 if (schemaMap != null) {
                     schemaMap.forEach((key, schema) -> components.addSchemas(key, schema));
@@ -1108,7 +1140,7 @@ protected Operation parseMethod(
 
         return operation;
     }
-
+    
     private boolean shouldIgnoreClass(String className) {
         if (StringUtils.isBlank(className)) {
             return true;