Add PublishSubscribeChannel

Add a PublishSubscribeChannel implementation of SubscribableChannel.

spring-context/src/main/java/org/springframework/messaging/PublishSubscribeChannel.java

+/*
+ * Copyright 2002-2013 the original author or authors.
+ *
+ * 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 org.springframework.messaging;
+
+import java.util.Set;
+import java.util.concurrent.CopyOnWriteArraySet;
+import java.util.concurrent.Executor;
+
+import org.springframework.util.Assert;
+
+/**
+ * A {@link SubscribableChannel} that sends messages to each of its subscribers. For a
+ * more feature complete implementation consider
+ * {@code org.springframework.integration.channel.PublishSubscribeChannel} from the
+ * Spring Integration project.
+ *
+ * @author Phillip Webb
+ */
+public class PublishSubscribeChannel implements SubscribableChannel {
+
+	private Executor executor;
+
+	private Set<MessageHandler> handlers = new CopyOnWriteArraySet<MessageHandler>();
+
+
+	/**
+	 * Create a new {@link PublishSubscribeChannel} instance where messages will be sent
+	 * in the callers thread.
+	 */
+	public PublishSubscribeChannel() {
+		this(null);
+	}
+
+	/**
+	 * Create a new {@link PublishSubscribeChannel} instance where messages will be sent
+	 * via the specified executor.
+	 * @param executor the executor used to send the message or {@code null} to execute in
+	 *        the callers thread.
+	 */
+	public PublishSubscribeChannel(Executor executor) {
+		this.executor = executor;
+	}
+
+	@Override
+	public boolean send(Message<?> message) {
+		return send(message, INDEFINITE_TIMEOUT);
+	}
+
+	@Override
+	public boolean send(Message<?> message, long timeout) {
+		Assert.notNull(message, "Message must not be null");
+		Assert.notNull(message.getPayload(), "Message payload must not be null");
+		for (final MessageHandler handler : this.handlers) {
+			dispatchToHandler(message, handler);
+		}
+		return true;
+	}
+
+	private void dispatchToHandler(final Message<?> message, final MessageHandler handler) {
+		if (this.executor == null) {
+			handler.handleMessage(message);
+		}
+		else {
+			this.executor.execute(new Runnable() {
+				@Override
+				public void run() {
+					handler.handleMessage(message);
+				}
+			});
+		}
+	}
+
+	@Override
+	public boolean subscribe(MessageHandler handler) {
+		return this.handlers.add(handler);
+	}
+
+	@Override
+	public boolean unsubscribe(MessageHandler handler) {
+		return this.handlers.remove(handler);
+	}
+
+}

spring-context/src/test/java/org/springframework/messaging/PublishSubscibeChannelTests.java

+/*
+ * Copyright 2002-2013 the original author or authors.
+ *
+ * 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 org.springframework.messaging;
+
+import java.util.concurrent.Executor;
+
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Captor;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+import org.springframework.messaging.support.MessageBuilder;
+
+import static org.hamcrest.Matchers.*;
+import static org.junit.Assert.*;
+import static org.mockito.BDDMockito.*;
+
+/**
+ * Tests for {@link PublishSubscribeChannel}.
+ *
+ * @author Phillip Webb
+ */
+public class PublishSubscibeChannelTests {
+
+	@Rule
+	public ExpectedException thrown = ExpectedException.none();
+
+
+	private PublishSubscribeChannel channel = new PublishSubscribeChannel();
+
+	@Mock
+	private MessageHandler handler;
+
+	private final Object payload = new Object();
+
+	private final Message<Object> message = MessageBuilder.withPayload(this.payload).build();
+
+	@Captor
+	private ArgumentCaptor<Runnable> runnableCaptor;
+
+
+	@Before
+	public void setup() {
+		MockitoAnnotations.initMocks(this);
+	}
+
+	@Test
+	public void messageMustNotBeNull() throws Exception {
+		thrown.expect(IllegalArgumentException.class);
+		thrown.expectMessage("Message must not be null");
+		this.channel.send(null);
+	}
+
+	@Test
+	public void payloadMustNotBeNull() throws Exception {
+		Message<?> message = mock(Message.class);
+		thrown.expect(IllegalArgumentException.class);
+		thrown.expectMessage("Message payload must not be null");
+		this.channel.send(message);
+	}
+
+	@Test
+	public void sendWithoutExecutor() {
+		this.channel.subscribe(this.handler);
+		this.channel.send(this.message);
+		verify(this.handler).handleMessage(this.message);
+	}
+
+	@Test
+	public void sendWithExecutor() throws Exception {
+		Executor executor = mock(Executor.class);
+		this.channel = new PublishSubscribeChannel(executor);
+		this.channel.subscribe(this.handler);
+		this.channel.send(this.message);
+		verify(executor).execute(this.runnableCaptor.capture());
+		verify(this.handler, never()).handleMessage(this.message);
+		this.runnableCaptor.getValue().run();
+		verify(this.handler).handleMessage(this.message);
+	}
+
+	@Test
+	public void subscribeTwice() throws Exception {
+		assertThat(this.channel.subscribe(this.handler), equalTo(true));
+		assertThat(this.channel.subscribe(this.handler), equalTo(false));
+		this.channel.send(this.message);
+		verify(this.handler, times(1)).handleMessage(this.message);
+	}
+
+	@Test
+	public void unsubscribeTwice() throws Exception {
+		this.channel.subscribe(this.handler);
+		assertThat(this.channel.unsubscribe(this.handler), equalTo(true));
+		assertThat(this.channel.unsubscribe(this.handler), equalTo(false));
+		this.channel.send(this.message);
+		verify(this.handler, never()).handleMessage(this.message);
+	}
+
+	@Test
+	public void failurePropagates() throws Exception {
+		RuntimeException ex = new RuntimeException();
+		willThrow(ex).given(this.handler).handleMessage(this.message);
+		MessageHandler secondHandler = mock(MessageHandler.class);
+		this.channel.subscribe(this.handler);
+		this.channel.subscribe(secondHandler);
+		try {
+			this.channel.send(message);
+		}
+		catch(RuntimeException actualException) {
+			assertThat(actualException, equalTo(ex));
+		}
+		verifyZeroInteractions(secondHandler);
+	}
+
+	@Test
+	public void concurrentModification() throws Exception {
+		this.channel.subscribe(new MessageHandler() {
+			@Override
+			public void handleMessage(Message<?> message) throws MessagingException {
+				channel.unsubscribe(handler);
+			}
+		});
+		this.channel.subscribe(this.handler);
+		this.channel.send(this.message);
+		verify(this.handler).handleMessage(this.message);
+	}
+
+}