WICKET-7148: Make deletion of Metadata in Application possible again (#…

…1101)

Co-authored-by: Schäfer, H.H. (Hans Hosea) <HansHosea.Schaefer@ing.de>

wicket-core/src/main/java/org/apache/wicket/Application.java

@@ -25,6 +25,7 @@
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.Supplier;
+
 import org.apache.wicket.application.ComponentInitializationListenerCollection;
 import org.apache.wicket.application.ComponentInstantiationListenerCollection;
 import org.apache.wicket.application.ComponentOnAfterRenderListenerCollection;
@@ -512,7 +513,11 @@ public void logResponseTarget(final IRequestHandler requestTarget)
 	@Override
 	public final <T> Application setMetaData(final MetaDataKey<T> key, final T object)
 	{
-		metaData.put(key, object);
+		if (object == null) {
+			metaData.remove(key);
+		} else {
+			metaData.put(key, object);
+		}
 		return this;
 	}
 

wicket-core/src/test/java/org/apache/wicket/ApplicationMetadataTest.java

@@ -0,0 +1,65 @@
+/*
+ * 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
+ *
+ *      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 org.apache.wicket;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+import java.io.Serializable;
+
+import org.apache.wicket.mock.MockApplication;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Test cases for the <code>Application-Metadata</code> class.
+ *
+ * @author Hans Hosea Schaefer
+ */
+public class ApplicationMetadataTest {
+
+	private static final MetaDataKey<Serializable> MY_METADATA_KEY = new MetaDataKey<>() {};
+
+	@AfterEach
+	void detachThreadContext() {
+		ThreadContext.detach();
+	}
+
+	@Test
+	void metadataAdded() {
+		final MockApplication application = new MockApplication();
+		assertNull(application.getMetaData(MY_METADATA_KEY));
+		application.setMetaData(MY_METADATA_KEY, "I love wicket");
+		assertEquals("I love wicket", application.getMetaData(MY_METADATA_KEY));
+	}
+
+	@Test
+	void metadataReplaced() {
+		final MockApplication application = new MockApplication();
+		application.setMetaData(MY_METADATA_KEY, "I love wicket");
+		application.setMetaData(MY_METADATA_KEY, "I love Idea");
+		assertEquals("I love Idea", application.getMetaData(MY_METADATA_KEY));
+	}
+
+	@Test
+	void metadataRemoved() {
+		final MockApplication application = new MockApplication();
+		application.setMetaData(MY_METADATA_KEY, "I love wicket");
+		application.setMetaData(MY_METADATA_KEY, null);
+		assertNull(application.getMetaData(MY_METADATA_KEY));
+	}
+}