NEW - bug 372432: [api] provide a generic list for managing listeners

https://bugs.eclipse.org/bugs/show_bug.cgi?id=372432

Change-Id: I6671363039aae57826a1537ab5d6ef6479c1f959

3 files changed, 218 insertions, 0 deletions

diff --git a/org.eclipse.mylyn.commons.core/src/org/eclipse/mylyn/commons/core/CommonListenerList.java b/org.eclipse.mylyn.commons.core/src/org/eclipse/mylyn/commons/core/CommonListenerList.java
new file mode 100644
index 0000000..2138160
--- a/dev/null
+++ b/org.eclipse.mylyn.commons.core/src/org/eclipse/mylyn/commons/core/CommonListenerList.java
@@ -0,0 +1,106 @@
+/*******************************************************************************
+ * Copyright (c) 2012 Tasktop Technologies and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Tasktop Technologies - initial API and implementation
+ *******************************************************************************/
+
+package org.eclipse.mylyn.commons.core;
+
+import java.util.Iterator;
+import java.util.concurrent.CopyOnWriteArrayList;
+
+import org.eclipse.core.runtime.Assert;
+import org.eclipse.core.runtime.ISafeRunnable;
+import org.eclipse.core.runtime.IStatus;
+import org.eclipse.core.runtime.SafeRunner;
+import org.eclipse.core.runtime.Status;
+import org.eclipse.osgi.util.NLS;
+
+/**
+ * A list like class for managing listeners. It is safe to call this class from different threads concurrently.
+ * 
+ * @since 3.7
+ */
+public class CommonListenerList<T> implements Iterable<T> {
+
+	/**
+	 * Subclasses should extend to not
+	 */
+	public static abstract class Notifier<T> {
+
+		/**
+		 * Fires an event to <code>listener</code>.
+		 * 
+		 * @param listener
+		 *            the listener to be notified
+		 * @throws Exception
+		 *             indicates a unrecoverable problem with <code>listener</code>
+		 */
+		public abstract void run(T listener) throws Exception;
+
+	}
+
+	private final CopyOnWriteArrayList<T> listeners;
+
+	private final String pluginId;
+
+	/**
+	 * Constructs an empty list.
+	 * 
+	 * @param pluginId
+	 *            the ID of the bundle that is managing this instance
+	 */
+	public CommonListenerList(String pluginId) {
+		Assert.isNotNull(pluginId);
+		this.pluginId = pluginId;
+		this.listeners = new CopyOnWriteArrayList<T>();
+	}
+
+	/**
+	 * Adds <code>listener</code> to the list of listeners.
+	 */
+	public void add(T listener) {
+		Assert.isNotNull(listener);
+		listeners.addIfAbsent(listener);
+	}
+
+	/**
+	 * Iterates over the list of listeners.
+	 */
+	public Iterator<T> iterator() {
+		return listeners.iterator();
+	}
+
+	/**
+	 * Invokes <code>runnable</code> for each listener. If {@link Notifier#run(Object)} throws an exception the
+	 * corresponding listener is removed from the list and a message is logged.
+	 */
+	public void notify(final Notifier<T> runnable) {
+		for (final T listener : listeners) {
+			SafeRunner.run(new ISafeRunnable() {
+				public void handleException(Throwable e) {
+					StatusHandler.log(new Status(IStatus.ERROR, pluginId, NLS.bind(
+							"Unexpected error notifying listener {0}", listener.getClass()), e)); //$NON-NLS-1$
+					remove(listener);
+				}
+
+				public void run() throws Exception {
+					runnable.run(listener);
+				}
+			});
+		}
+	}
+
+	/**
+	 * Removes <code>listener</code> to the list of listeners.
+	 */
+	public void remove(T listener) {
+		listeners.remove(listener);
+	}
+
+}
diff --git a/org.eclipse.mylyn.commons.tests/src/org/eclipse/mylyn/commons/tests/AllCommonsTests.java b/org.eclipse.mylyn.commons.tests/src/org/eclipse/mylyn/commons/tests/AllCommonsTests.java
index 720f47a..1f4210d 100644
--- a/org.eclipse.mylyn.commons.tests/src/org/eclipse/mylyn/commons/tests/AllCommonsTests.java
+++ b/org.eclipse.mylyn.commons.tests/src/org/eclipse/mylyn/commons/tests/AllCommonsTests.java
@@ -15,6 +15,7 @@ import junit.framework.Test;
 import junit.framework.TestSuite;
 
 import org.eclipse.mylyn.commons.tests.core.AuthenticatedProxyTest;
+import org.eclipse.mylyn.commons.tests.core.CommonListenerListTest;
 import org.eclipse.mylyn.commons.tests.core.CoreUtilTest;
 import org.eclipse.mylyn.commons.tests.core.ExtensionPointReaderTest;
 import org.eclipse.mylyn.commons.tests.net.NetUtilTest;
@@ -40,6 +41,7 @@ public class AllCommonsTests {
 		suite.addTestSuite(TimeoutInputStreamTest.class);
 		suite.addTestSuite(BrowserUtilTest.class);
 		suite.addTestSuite(ExtensionPointReaderTest.class);
+		suite.addTestSuite(CommonListenerListTest.class);
 		return suite;
 	}
 
diff --git a/org.eclipse.mylyn.commons.tests/src/org/eclipse/mylyn/commons/tests/core/CommonListenerListTest.java b/org.eclipse.mylyn.commons.tests/src/org/eclipse/mylyn/commons/tests/core/CommonListenerListTest.java
new file mode 100644
index 0000000..28704fb
--- a/dev/null
+++ b/org.eclipse.mylyn.commons.tests/src/org/eclipse/mylyn/commons/tests/core/CommonListenerListTest.java
@@ -0,0 +1,110 @@
+/*******************************************************************************
+ * Copyright (c) 2012 Tasktop Technologies and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Tasktop Technologies - initial API and implementation
+ *******************************************************************************/
+
+package org.eclipse.mylyn.commons.tests.core;
+
+import java.util.Iterator;
+
+import junit.framework.TestCase;
+
+import org.eclipse.mylyn.commons.core.CommonListenerList;
+import org.eclipse.mylyn.commons.core.CommonListenerList.Notifier;
+
+/**
+ * @author Steffen Pingel
+ */
+public class CommonListenerListTest extends TestCase {
+
+	private class Listener {
+
+		private boolean notified;
+
+	}
+
+	public void testAddRemove() {
+		final Listener addedListener = new Listener();
+		CommonListenerList<Listener> list = new CommonListenerList<Listener>("a");
+
+		list.add(addedListener);
+		assertTrue(list.iterator().hasNext());
+		assertSame(addedListener, list.iterator().next());
+
+		list.remove(addedListener);
+		assertFalse(list.iterator().hasNext());
+	}
+
+	public void testAddTwice() {
+		final Listener addedListener = new Listener();
+		CommonListenerList<Listener> list = new CommonListenerList<Listener>("a");
+		list.add(addedListener);
+		list.add(addedListener);
+
+		Iterator<Listener> iterator = list.iterator();
+		assertTrue(iterator.hasNext());
+		iterator.next();
+		assertFalse(iterator.hasNext());
+	}
+
+	public void testIterator() {
+		final Listener listener1 = new Listener();
+		final Listener listener2 = new Listener();
+		final Listener listener3 = new Listener();
+		CommonListenerList<Listener> list = new CommonListenerList<Listener>("a");
+		list.add(listener1);
+		list.add(listener2);
+		list.add(listener3);
+		list.add(listener1);
+
+		Iterator<Listener> iterator = list.iterator();
+		assertSame(listener1, iterator.next());
+		assertSame(listener2, iterator.next());
+		assertSame(listener3, iterator.next());
+	}
+
+	public void testNotify() {
+		final Listener addedListener = new Listener();
+		CommonListenerList<Listener> list = new CommonListenerList<Listener>("a");
+		list.add(addedListener);
+
+		list.notify(new Notifier<Listener>() {
+			@Override
+			public void run(Listener listener) throws Exception {
+				assertSame(listener, addedListener);
+				addedListener.notified = true;
+			}
+		});
+		assertTrue(addedListener.notified);
+	}
+
+	public void testNotifyException() {
+		final Listener addedListener = new Listener();
+		CommonListenerList<Listener> list = new CommonListenerList<Listener>("a");
+		list.add(addedListener);
+
+		list.notify(new Notifier<Listener>() {
+			@Override
+			public void run(Listener listener) throws Exception {
+				// should cause listener to get removed
+				throw new LinkageError();
+			}
+		});
+		assertFalse(list.iterator().hasNext());
+
+		list.notify(new Notifier<Listener>() {
+			@Override
+			public void run(Listener listener) throws Exception {
+				addedListener.notified = true;
+			}
+		});
+		assertFalse(addedListener.notified);
+	}
+
+}