[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 +733,15 @@ 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);
+                                }
                             }
                         }
                     }
@@ -764,14 +768,7 @@ public void preprocessOpenAPI(OpenAPI openAPI) {
                 Schema s = e.getValue();
                 String nOneOf = toModelName(n + "OneOf");
                 if (ModelUtils.isComposedSchema(s)) {
-                    if (e.getKey().contains("/")) {
-                        // if this is property schema, we also need to generate the oneOf interface model
-                        addOneOfNameExtension((ComposedSchema) s, nOneOf);
-                        addOneOfInterfaceModel((ComposedSchema) s, nOneOf);
-                    } else {
-                        // else this is a component schema, so we will just use that as the oneOf interface model
-                        addOneOfNameExtension((ComposedSchema) s, n);
-                    }
+                    addOneOfForComposedSchema(e, n, (ComposedSchema) s, nOneOf);
                 } else if (ModelUtils.isArraySchema(s)) {
                     Schema items = ((ArraySchema) s).getItems();
                     if (ModelUtils.isComposedSchema(items)) {
@@ -789,6 +786,18 @@ public void preprocessOpenAPI(OpenAPI openAPI) {
         }
     }
 
+    protected void addOneOfForComposedSchema(Entry<String, Schema> stringSchemaEntry, String modelName, ComposedSchema composedSchema,
+        String nOneOf) {
+        if (stringSchemaEntry.getKey().contains("/")) {
+            // if this is property schema, we also need to generate the oneOf interface model
+            addOneOfNameExtension(composedSchema, nOneOf);
+            addOneOfInterfaceModel(composedSchema, nOneOf);
+        } else {
+            // else this is a component schema, so we will just use that as the oneOf interface model
+            addOneOfNameExtension(composedSchema, modelName);
+        }
+    }
+
     // override with any special handling of the entire OpenAPI spec document
     @SuppressWarnings("unused")
     public void processOpenAPI(OpenAPI openAPI) {
@@ -5444,8 +5453,8 @@ public CodegenParameter fromRequestBody(RequestBody body, Set<String> imports, S
                                     "'application/x-www-form-urlencoded' or 'multipart/?'");
                             LOGGER.warn("schema: " + schema);
                             LOGGER.warn("codegenModel is null. Default to UNKNOWN_BASE_TYPE");
-                            codegenModelName = "UNKNOWN_BASE_TYPE";
                             codegenModelDescription = "UNKNOWN_DESCRIPTION";
+                            codegenModelName = getCodegenModelName(codegenProperty);
                         }
 
                         if (StringUtils.isEmpty(bodyParameterName)) {
@@ -5461,7 +5470,7 @@ public CodegenParameter fromRequestBody(RequestBody body, Set<String> imports, S
                         imports.add(codegenParameter.baseType);
 
                         if (codegenProperty.complexType != null) {
-                            imports.add(codegenProperty.complexType);
+                            addAdditionalImports(imports, codegenProperty.complexType);
                         }
                     }
                 }
@@ -5510,6 +5519,14 @@ public CodegenParameter fromRequestBody(RequestBody body, Set<String> imports, S
         return codegenParameter;
     }
 
+    protected void addAdditionalImports(Set<String> imports, String complexType) {
+        imports.add(complexType);
+    }
+
+    protected String getCodegenModelName(CodegenProperty codegenProperty) {
+        return "UNKNOWN_BASE_TYPE";
+    }
+
     protected void addOption(String key, String description, String defaultValue) {
         CliOption option = new CliOption(key, description);
         if (defaultValue != null)

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

@@ -21,6 +21,9 @@
 import io.swagger.v3.oas.models.OpenAPI;
 import io.swagger.v3.oas.models.Operation;
 import io.swagger.v3.oas.models.PathItem;
+import io.swagger.v3.oas.models.media.ComposedSchema;
+import io.swagger.v3.oas.models.media.Schema;
+import java.util.Map.Entry;
 import org.apache.commons.lang3.tuple.Pair;
 import org.openapitools.codegen.*;
 import org.openapitools.codegen.languages.features.BeanValidationFeatures;
@@ -233,7 +236,7 @@ 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
@@ -581,6 +584,34 @@ public void preprocessOpenAPI(OpenAPI openAPI) {
         }
     }
 
+    @Override
+    protected void addOneOfForComposedSchema(Entry<String, Schema> stringSchemaEntry, String modelName, ComposedSchema composedSchema,
+        String nOneOf){
+        if (useOneOfInterfaces) {
+            // if this is property schema, we also need to generate the oneOf interface model
+            addOneOfNameExtension(composedSchema, nOneOf);
+            addOneOfInterfaceModel(composedSchema, nOneOf);
+        } else {
+            super.addOneOfForComposedSchema(stringSchemaEntry, modelName, composedSchema, nOneOf);
+        }
+    }
+
+    @Override
+    protected String getCodegenModelName(CodegenProperty codegenProperty) {
+        if (useOneOfInterfaces){
+            return codegenProperty.getComplexType();
+        } else {
+            return super.getCodegenModelName(codegenProperty);
+        }
+    }
+
+    @Override
+    protected void addAdditionalImports(Set<String> imports, String complexType) {
+        if (!useOneOfInterfaces){
+            super.addAdditionalImports(imports, complexType);
+        }
+    }
+
     @Override
     public Map<String, Object> postProcessOperationsWithModels(Map<String, Object> objs, List<Object> allModels) {
         Map<String, Object> operations = (Map<String, Object>) objs.get("operations");
@@ -898,4 +929,16 @@ 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}}
+}