/**
 * Copyright 2007-2016, Kaazing Corporation. All rights reserved.
 *
 * 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.apache.mina.handler.demux;

import org.apache.mina.core.session.IoSession;

/**
 * A handler interface that {@link DemuxingIoHandler} forwards
 * <tt>messageReceived</tt> or <tt>messageSent</tt> events to.  You have to
 * register your handler with the type of the message you want to get notified
 * using {@link DemuxingIoHandler#addReceivedMessageHandler(Class, MessageHandler)}
 * or {@link DemuxingIoHandler#addSentMessageHandler(Class, MessageHandler)}.
 *
 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
 */
public interface MessageHandler<E> {
    /**
     * A {@link MessageHandler} that does nothing.  This is useful when
     * you want to ignore a message of a specific type silently.
     */
    MessageHandler<Object> NOOP = new MessageHandler<Object>() {
        public void handleMessage(IoSession session, Object message) {
            // Do nothing
        }
    };

    /**
     * Invoked when the specific type of message is received from or sent to
     * the specified <code>session</code>.
     * 
     * @param session the associated {@link IoSession}
     * @param message the message to decode. Its type is set by the implementation
     * @throws Exception if there is an error during the message processing
     */
    void handleMessage(IoSession session, E message) throws Exception;
}