refactor: remove unnecessary lock, fix deprecated API, guard null in …

src/main/java/com/onehippo/cms7/genericresource/entitybuilder/GenericResourceEntityBuilder.java

@@ -32,20 +32,12 @@ public abstract class GenericResourceEntityBuilder {
 
     private static final String NAME = GenericResourceEntityBuilder.class.getName();
 
-    private static final Object lock = new Object();
-
     public static GenericResourceEntityBuilder get(final HstRequestContext requestContext) {
         GenericResourceEntityBuilder builder = (GenericResourceEntityBuilder) requestContext.getAttribute(NAME);
 
         if (builder == null) {
-            synchronized (lock) {
-                builder = (GenericResourceEntityBuilder) requestContext.getAttribute(NAME);
-
-                if (builder == null) {
-                    builder = new DefaultGenericResourceEntityBuilder();
-                    requestContext.setAttribute(NAME, builder);
-                }
-            }
+            builder = new DefaultGenericResourceEntityBuilder();
+            requestContext.setAttribute(NAME, builder);
         }
 
         return builder;

src/main/java/com/onehippo/cms7/genericresource/entitybuilder/container/GenericResourceEntityAggregationValve.java

@@ -21,7 +21,6 @@
 
 import jakarta.servlet.http.HttpServletResponse;
 
-import org.apache.commons.io.IOUtils;
 import org.apache.commons.lang3.StringUtils;
 import org.apache.commons.lang3.Strings;
 import org.hippoecm.hst.container.RequestContextProvider;
@@ -89,18 +88,14 @@ protected void processWindowsRender(final HstContainerConfig requestContainerCon
 
         GenericResourceEntityBuilder builder = GenericResourceEntityBuilder.get(requestContext);
 
-        PrintWriter writer = null;
+        response.setContentType("application/json");
 
-        try {
-            response.setContentType("application/json");
-            writer = response.getWriter();
+        try (PrintWriter writer = response.getWriter()) {
             builder.write(getObjectMapper(), writer);
         } catch (GenericResourceEntityBuilderException e) {
             log.warn("Failed to generate json.", e);
         } catch (IOException e) {
             log.warn("Failed to write json.", e);
-        } finally {
-            IOUtils.closeQuietly(writer);
         }
     }
 }

src/main/java/com/onehippo/cms7/genericresource/entitybuilder/jackson/HstLinkSerializer.java

@@ -39,6 +39,11 @@ public HstLinkSerializer(Class<HstLink> type) {
 
     @Override
     public void serialize(HstLink value, JsonGenerator gen, SerializerProvider provider) throws IOException {
+        if (value == null) {
+            gen.writeNull();
+            return;
+        }
+
         final HstRequestContext requestContext = RequestContextProvider.get();
 
         gen.writeStartObject();

src/test/java/com/onehippo/cms7/genericresource/entitybuilder/GenericResourceEntityBuilderTest.java

@@ -16,6 +16,9 @@
 import org.junit.Test;
 import org.onehippo.repository.mock.MockNode;
 
+import static org.junit.Assert.assertNotSame;
+import static org.junit.Assert.assertSame;
+
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.onehippo.cms7.genericresource.entitybuilder.jackson.DefaultJsonIgnoreTypeMixin;
 import com.onehippo.cms7.genericresource.entitybuilder.jackson.HstBeansExcludingObjectMapperDecorator;
@@ -37,6 +40,20 @@ public void setUp() throws Exception {
         objectMapper = decorator.decorate(new ObjectMapper());
     }
 
+    @Test
+    public void get_returnsSameInstanceForSameRequestContext() {
+        GenericResourceEntityBuilder first = GenericResourceEntityBuilder.get(requestContext);
+        GenericResourceEntityBuilder second = GenericResourceEntityBuilder.get(requestContext);
+        assertSame(first, second);
+    }
+
+    @Test
+    public void get_returnsNewInstanceForDifferentRequestContext() {
+        GenericResourceEntityBuilder first = GenericResourceEntityBuilder.get(requestContext);
+        GenericResourceEntityBuilder second = GenericResourceEntityBuilder.get(new MockHstRequestContext());
+        assertNotSame(first, second);
+    }
+
     @Test
     public void testJsonOut() throws Exception {
         GenericResourceEntityBuilder builder = GenericResourceEntityBuilder.get(requestContext);

src/test/java/com/onehippo/cms7/genericresource/entitybuilder/jackson/HstLinkSerializerTest.java

@@ -0,0 +1,41 @@
+/*
+ *  Copyright 2017-2025 BloomReach, Inc. (https://www.bloomreach.com)
+ *
+ *  Licensed 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
+ *
+ *       http://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 com.onehippo.cms7.genericresource.entitybuilder.jackson;
+
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.databind.SerializerProvider;
+import org.junit.Test;
+
+import static org.easymock.EasyMock.createMock;
+import static org.easymock.EasyMock.replay;
+import static org.easymock.EasyMock.verify;
+
+public class HstLinkSerializerTest {
+
+    @Test
+    public void serialize_nullValue_writesJsonNull() throws Exception {
+        JsonGenerator gen = createMock(JsonGenerator.class);
+        SerializerProvider provider = createMock(SerializerProvider.class);
+
+        gen.writeNull();
+
+        replay(gen, provider);
+
+        new HstLinkSerializer().serialize(null, gen, provider);
+
+        verify(gen, provider);
+    }
+}