Add SubscribableChannel and ReactorMessageChannel

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

@@ -0,0 +1,51 @@
+/*
+ * 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;
+
+
+/**
+ * Base interface for any component that handles Messages.
+ *
+ * @author Mark Fisher
+ * @author Iwein Fuld
+ * @since 4.0
+ */
+public interface MessageHandler {
+
+	/**
+	 * TODO: support exceptions?
+	 *
+	 * Handles the message if possible. If the handler cannot deal with the
+	 * message this will result in a <code>MessageRejectedException</code> e.g.
+	 * in case of a Selective Consumer. When a consumer tries to handle a
+	 * message, but fails to do so, a <code>MessageHandlingException</code> is
+	 * thrown. In the last case it is recommended to treat the message as tainted
+	 * and go into an error scenario.
+	 * <p>
+	 * When the handling results in a failure of another message being sent
+	 * (e.g. a "reply" message), that failure  will trigger a
+	 * <code>MessageDeliveryException</code>.
+	 *
+	 * @param message the message to be handled
+	 * @throws org.springframework.integration.MessageRejectedException if the handler doesn't accept the message
+	 * @throws org.springframework.integration.MessageHandlingException when something fails during the handling
+	 * @throws org.springframework.integration.MessageDeliveryException when this handler failed to deliver the
+	 * reply related to the handling of the message
+	 */
+	void handleMessage(Message<?> message) throws MessagingException;
+
+}

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

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+/*
+ * 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;
+
+
+/**
+ * Interface for any MessageChannel implementation that accepts subscribers.
+ * The subscribers must implement the {@link MessageHandler} interface and
+ * will be invoked when a Message is available.
+ *
+ * @author Mark Fisher
+ * @since 4.0
+ */
+public interface SubscribableChannel extends MessageChannel {
+
+	/**
+	 * Register a {@link MessageHandler} as a subscriber to this channel.
+	 */
+	boolean subscribe(MessageHandler handler);
+
+	/**
+	 * Remove a {@link MessageHandler} from the subscribers of this channel.
+	 */
+	boolean unsubscribe(MessageHandler handler);
+
+}