7.1.x Fix Enum JSON/XML Serialization for Round-Trip Compatibility

grails-converters/src/main/groovy/org/grails/web/converters/configuration/ConvertersConfigurationInitializer.java

@@ -95,11 +95,19 @@ private void initJSONConfiguration() {
         marshallers.add(new org.grails.web.converters.marshaller.json.ByteArrayMarshaller());
         marshallers.add(new org.grails.web.converters.marshaller.json.CollectionMarshaller());
         marshallers.add(new org.grails.web.converters.marshaller.json.MapMarshaller());
-        marshallers.add(new org.grails.web.converters.marshaller.json.EnumMarshaller());
-        marshallers.add(new org.grails.web.converters.marshaller.ProxyUnwrappingMarshaller<>());
 
         Config grailsConfig = getGrailsConfig();
 
+        // Register enum marshaller - defaults to legacy for backward compatibility (will change in Grails 8.0)
+        String jsonEnumFormat = grailsConfig.getProperty("grails.converters.json.enum.format", String.class, "default");
+        if ("simple".equals(jsonEnumFormat)) {
+            marshallers.add(new org.grails.web.converters.marshaller.json.SimpleEnumMarshaller());
+        } else {
+            marshallers.add(new org.grails.web.converters.marshaller.json.EnumMarshaller());
+        }
+
+        marshallers.add(new org.grails.web.converters.marshaller.ProxyUnwrappingMarshaller<>());
+
         if ("javascript".equals(grailsConfig.getProperty(SETTING_CONVERTERS_JSON_DATE, String.class, "default", Arrays.asList("javascript", "default")))) {
             if (LOG.isDebugEnabled()) {
                 LOG.debug("Using Javascript JSON Date Marshaller.");
@@ -177,14 +185,22 @@ private void initXMLConfiguration() {
         marshallers.add(new org.grails.web.converters.marshaller.xml.ArrayMarshaller());
         marshallers.add(new org.grails.web.converters.marshaller.xml.CollectionMarshaller());
         marshallers.add(new org.grails.web.converters.marshaller.xml.MapMarshaller());
-        marshallers.add(new org.grails.web.converters.marshaller.xml.EnumMarshaller());
+
+        Config grailsConfig = getGrailsConfig();
+
+        // Register enum marshaller - defaults to legacy for backward compatibility (will change in Grails 8.0)
+        String xmlEnumFormat = grailsConfig.getProperty("grails.converters.xml.enum.format", String.class, "default");
+        if ("simple".equals(xmlEnumFormat)) {
+            marshallers.add(new org.grails.web.converters.marshaller.xml.SimpleEnumMarshaller());
+        } else {
+            marshallers.add(new org.grails.web.converters.marshaller.xml.EnumMarshaller());
+        }
+
         marshallers.add(new org.grails.web.converters.marshaller.xml.DateMarshaller());
         marshallers.add(new ProxyUnwrappingMarshaller<>());
         marshallers.add(new org.grails.web.converters.marshaller.xml.ToStringBeanMarshaller());
         ProxyHandler proxyHandler = getProxyHandler();
 
-        Config grailsConfig = getGrailsConfig();
-
         boolean includeDomainVersion = includeDomainVersionProperty(grailsConfig, "xml");
         if (grailsConfig.getProperty(SETTING_CONVERTERS_XML_DEEP, Boolean.class, false)) {
             marshallers.add(new org.grails.web.converters.marshaller.xml.DeepDomainClassMarshaller(includeDomainVersion, proxyHandler, grailsApplication));

grails-converters/src/main/groovy/org/grails/web/converters/marshaller/json/EnumMarshaller.java

@@ -30,7 +30,11 @@
 /**
  * @author Siegfried Puchbauer
  * @since 1.1
+ * @deprecated As of 7.0.2, replaced by {@link SimpleEnumMarshaller} for round-trip compatibility.
+ *             This marshaller will no longer be registered by default in Grails 8.0.
+ *             To opt-in to the new behavior now, set {@code grails.converters.json.enum.format=simple} in application.yml.
  */
+@Deprecated(forRemoval = true, since = "7.0.2")
 public class EnumMarshaller implements ObjectMarshaller<JSON> {
 
     public boolean supports(Object object) {

grails-converters/src/main/groovy/org/grails/web/converters/marshaller/json/SimpleEnumMarshaller.java

@@ -0,0 +1,58 @@
+/*
+ *  Licensed to the Apache Software Foundation (ASF) under one
+ *  or more contributor license agreements.  See the NOTICE file
+ *  distributed with this work for additional information
+ *  regarding copyright ownership.  The ASF licenses this file
+ *  to you under the Apache License, Version 2.0 (the
+ *  "License"); you may not use this file except in compliance
+ *  with the License.  You may obtain a copy of the License at
+ *
+ *    https://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing,
+ *  software distributed under the License is distributed on an
+ *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ *  KIND, either express or implied.  See the License for the
+ *  specific language governing permissions and limitations
+ *  under the License.
+ */
+package org.grails.web.converters.marshaller.json;
+
+import java.lang.reflect.Method;
+
+import org.springframework.beans.BeanUtils;
+
+import grails.converters.JSON;
+import org.grails.web.converters.exceptions.ConverterException;
+import org.grails.web.converters.marshaller.ObjectMarshaller;
+
+/**
+ * Marshals enums as simple string values (just the enum name) for symmetric serialization/deserialization.
+ * This provides round-trip compatibility where POSTing JSON returns the same format when GETting.
+ *
+ * @since 7.0.2
+ */
+public class SimpleEnumMarshaller implements ObjectMarshaller<JSON> {
+
+    public boolean supports(Object object) {
+        return object.getClass().isEnum();
+    }
+
+    public void marshalObject(Object en, JSON json) throws ConverterException {
+        try {
+            Method nameMethod = BeanUtils.findDeclaredMethod(en.getClass(), "name");
+            try {
+                json.convertAnother(nameMethod.invoke(en));
+            }
+            catch (Exception e) {
+                json.convertAnother("");
+            }
+        }
+        catch (ConverterException ce) {
+            throw ce;
+        }
+        catch (Exception e) {
+            throw new ConverterException("Error converting Enum with class " + en.getClass().getName(), e);
+        }
+    }
+}

grails-converters/src/main/groovy/org/grails/web/converters/marshaller/xml/EnumMarshaller.java

@@ -29,7 +29,11 @@
 /**
  * @author Siegfried Puchbauer
  * @since 1.1
+ * @deprecated As of 7.0.2, replaced by {@link SimpleEnumMarshaller} for round-trip compatibility.
+ *             This marshaller will no longer be registered by default in Grails 8.0.
+ *             To opt-in to the new behavior now, set {@code grails.converters.xml.enum.format=simple} in application.yml.
  */
+@Deprecated(forRemoval = true, since = "7.0.2")
 public class EnumMarshaller implements ObjectMarshaller<XML> {
 
     public boolean supports(Object object) {

grails-converters/src/main/groovy/org/grails/web/converters/marshaller/xml/SimpleEnumMarshaller.java

@@ -0,0 +1,58 @@
+/*
+ *  Licensed to the Apache Software Foundation (ASF) under one
+ *  or more contributor license agreements.  See the NOTICE file
+ *  distributed with this work for additional information
+ *  regarding copyright ownership.  The ASF licenses this file
+ *  to you under the Apache License, Version 2.0 (the
+ *  "License"); you may not use this file except in compliance
+ *  with the License.  You may obtain a copy of the License at
+ *
+ *    https://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing,
+ *  software distributed under the License is distributed on an
+ *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ *  KIND, either express or implied.  See the License for the
+ *  specific language governing permissions and limitations
+ *  under the License.
+ */
+package org.grails.web.converters.marshaller.xml;
+
+import java.lang.reflect.Method;
+
+import org.springframework.beans.BeanUtils;
+
+import grails.converters.XML;
+import org.grails.web.converters.exceptions.ConverterException;
+import org.grails.web.converters.marshaller.ObjectMarshaller;
+
+/**
+ * Marshals enums as simple string values (just the enum name) for symmetric serialization/deserialization.
+ * This provides round-trip compatibility where POSTing XML returns the same format when GETting.
+ *
+ * @since 7.0.2
+ */
+public class SimpleEnumMarshaller implements ObjectMarshaller<XML> {
+
+    public boolean supports(Object object) {
+        return object.getClass().isEnum();
+    }
+
+    public void marshalObject(Object en, XML xml) throws ConverterException {
+        try {
+            Method nameMethod = BeanUtils.findDeclaredMethod(en.getClass(), "name");
+            try {
+                xml.chars(nameMethod.invoke(en).toString());
+            }
+            catch (Exception e) {
+                // ignored
+            }
+        }
+        catch (ConverterException ce) {
+            throw ce;
+        }
+        catch (Exception e) {
+            throw new ConverterException("Error converting Enum with class " + en.getClass().getName(), e);
+        }
+    }
+}

grails-test-suite-web/src/test/groovy/org/grails/web/converters/JSONConverterTests.groovy

@@ -103,6 +103,26 @@ class JSONConverterTests extends Specification implements ControllerUnitTest<JSO
         json.size() == 2
     }
 
+    void testJSONEnumConvertingWithSimpleMarshaller() {
+        given:
+        JSON.createNamedConfig('simple') {
+            it.registerObjectMarshaller(new org.grails.web.converters.marshaller.json.SimpleEnumMarshaller())
+        }
+        JSON.use('simple')
+
+        when:
+        def enumInstance = Role.HEAD
+        params.e = enumInstance
+        controller.testEnumInMap()
+        def jsonString = response.contentAsString
+        def json = response.json
+
+        then:
+        json.size() == 1
+        jsonString == '{"value":"HEAD"}'
+        json.value == "HEAD"
+    }
+
     // GRAILS-11513
     void testStringsWithQuotes() {
         when:
@@ -196,6 +216,10 @@ class JSONConverterController {
        render params.e as JSON
    }
 
+   def testEnumInMap = {
+       render([value: params.e] as JSON)
+   }
+
     def testNullValues = {
         def descriptors = [:]
         descriptors.put(null,null)