[Spring][server] oneOf Polymorphism support for spring boot

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

@@ -710,7 +710,7 @@ public void postProcessParameter(CodegenParameter parameter) {
     //override with any special handling of the entire OpenAPI spec document
     @SuppressWarnings("unused")
     public void preprocessOpenAPI(OpenAPI openAPI) {
-        if (useOneOfInterfaces) {
+        if (useOneOfInterfaces && openAPI.getComponents() != null) {
             // we process the openapi schema here to find oneOf schemas and create interface models for them
             Map<String, Schema> schemas = new HashMap<String, Schema>(openAPI.getComponents().getSchemas());
             if (schemas == null) {
@@ -733,11 +733,13 @@ public void preprocessOpenAPI(OpenAPI openAPI) {
                             schemas.put(opId, requestSchema);
                         }
                         // process all response bodies
-                        for (Map.Entry<String, ApiResponse> ar : op.getValue().getResponses().entrySet()) {
-                            ApiResponse a = ModelUtils.getReferencedApiResponse(openAPI, ar.getValue());
-                            Schema responseSchema = ModelUtils.getSchemaFromResponse(a);
-                            if (responseSchema != null) {
-                                schemas.put(opId + ar.getKey(), responseSchema);
+                        if (op.getValue().getResponses() != null){
+                            for (Map.Entry<String, ApiResponse> ar : op.getValue().getResponses().entrySet()) {
+                                ApiResponse a = ModelUtils.getReferencedApiResponse(openAPI, ar.getValue());
+                                Schema responseSchema = ModelUtils.getSchemaFromResponse(a);
+                                if (responseSchema != null) {
+                                    schemas.put(opId + ar.getKey(), responseSchema);
+                                }
                             }
                         }
                     }
@@ -5425,6 +5427,9 @@ public CodegenParameter fromRequestBody(RequestBody body, Set<String> imports, S
                             LOGGER.warn("codegenModel is null. Default to UNKNOWN_BASE_TYPE");
                             codegenModelName = "UNKNOWN_BASE_TYPE";
                             codegenModelDescription = "UNKNOWN_DESCRIPTION";
+                            if (useOneOfInterfaces && templateDir.equals("JavaSpring")){
+                                codegenModelName = codegenProperty.getComplexType()+"OneOf";
+                            }
                         }
 
                         if (StringUtils.isEmpty(bodyParameterName)) {
@@ -5439,7 +5444,7 @@ public CodegenParameter fromRequestBody(RequestBody body, Set<String> imports, S
                         codegenParameter.description = codegenModelDescription;
                         imports.add(codegenParameter.baseType);
 
-                        if (codegenProperty.complexType != null) {
+                        if (codegenProperty.complexType != null && (useOneOfInterfaces && !templateDir.equals("JavaSpring"))) {
                             imports.add(codegenProperty.complexType);
                         }
                     }

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

@@ -233,7 +233,7 @@ public void processOpts() {
         }
 
         super.processOpts();
-
+        useOneOfInterfaces = true;
         // clear model and api doc template as this codegen
         // does not support auto-generated markdown doc at the moment
         //TODO: add doc templates
@@ -898,4 +898,16 @@ public void postProcessParameter(CodegenParameter p) {
         }
     }
 
-}
+    @Override
+    public void addImportsToOneOfInterface(List<Map<String, String>> imports) {
+        for (String i : Arrays.asList("JsonSubTypes", "JsonTypeInfo")) {
+            Map<String, String> oneImport = new HashMap<String, String>() {{
+                put("import", importMapping.get(i));
+            }};
+            if (!imports.contains(oneImport)) {
+                imports.add(oneImport);
+            }
+        }
+    }
+
+}

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

@@ -35,7 +35,7 @@ import org.springframework.hateoas.RepresentationModel;
 {{>enumOuterClass}}
 {{/isEnum}}
 {{^isEnum}}
-{{>pojo}}
+{{#vendorExtensions.x-is-one-of-interface}}{{>oneof_interface}}{{/vendorExtensions.x-is-one-of-interface}}{{^vendorExtensions.x-is-one-of-interface}}{{>pojo}}{{/vendorExtensions.x-is-one-of-interface}}
 {{/isEnum}}
 {{/model}}
 {{/models}}

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

@@ -0,0 +1,6 @@
+{{>additionalModelTypeAnnotations}}{{>generatedAnnotation}}{{>typeInfoAnnotation}}{{>xmlAnnotation}}
+public interface {{classname}} {{#vendorExtensions.x-implements}}{{#-first}}extends {{{.}}}{{/-first}}{{^-first}}, {{{.}}}{{/-first}}{{/vendorExtensions.x-implements}} {
+    {{#discriminator}}
+    public {{propertyType}} {{propertyGetter}}();
+    {{/discriminator}}
+}