/*
 * Copyright 2013 The Netty Project
 *
 * The Netty Project 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 io.netty.channel;

import io.netty.util.ReferenceCountUtil;
import io.netty.util.internal.TypeParameterMatcher;

ChannelInboundHandlerAdapter which allows to explicit only handle a specific type of messages. For example here is an implementation which only handle String messages. 
 public class StringHandler extends SimpleChannelInboundHandler<String> { @Override protected void channelRead0(ChannelHandlerContext ctx, String message) throws Exception { System.out.println(message); } } 
 Be aware that depending of the constructor parameters it will release all handled messages by passing them to ReferenceCountUtil.release(Object). In this case you may need to use ReferenceCountUtil.retain(Object) if you pass the object to the next handler in the ChannelPipeline. 
Forward compatibility notice
 Please keep in mind that channelRead0(ChannelHandlerContext, Object) will be renamed to messageReceived(ChannelHandlerContext, I) in 5.0. 
/**
 * {@link ChannelInboundHandlerAdapter} which allows to explicit only handle a specific type of messages.
 *
 * For example here is an implementation which only handle {@link String} messages.
 *
 * <pre>
 *     public class StringHandler extends
 *             {@link SimpleChannelInboundHandler}&lt;{@link String}&gt; {
 *
 *         {@code @Override}
 *         protected void channelRead0({@link ChannelHandlerContext} ctx, {@link String} message)
 *                 throws {@link Exception} {
 *             System.out.println(message);
 *         }
 *     }
 * </pre>
 *
 * Be aware that depending of the constructor parameters it will release all handled messages by passing them to
 * {@link ReferenceCountUtil#release(Object)}. In this case you may need to use
 * {@link ReferenceCountUtil#retain(Object)} if you pass the object to the next handler in the {@link ChannelPipeline}.
 *
 * <h3>Forward compatibility notice</h3>
 * <p>
 * Please keep in mind that {@link #channelRead0(ChannelHandlerContext, I)} will be renamed to
 * {@code messageReceived(ChannelHandlerContext, I)} in 5.0.
 * </p>
 */
public abstract class SimpleChannelInboundHandler<I> extends ChannelInboundHandlerAdapter {

    private final TypeParameterMatcher matcher;
    private final boolean autoRelease;

    
see SimpleChannelInboundHandler(boolean) with true as boolean parameter. /**
     * see {@link #SimpleChannelInboundHandler(boolean)} with {@code true} as boolean parameter.
     */
    protected SimpleChannelInboundHandler() {
        this(true);
    }

    
Create a new instance which will try to detect the types to match out of the type parameter of the class.
Params:
autoRelease –  true if handled messages should be released automatically by passing them to ReferenceCountUtil.release(Object)./**
     * Create a new instance which will try to detect the types to match out of the type parameter of the class.
     *
     * @param autoRelease   {@code true} if handled messages should be released automatically by passing them to
     *                      {@link ReferenceCountUtil#release(Object)}.
     */
    protected SimpleChannelInboundHandler(boolean autoRelease) {
        matcher = TypeParameterMatcher.find(this, SimpleChannelInboundHandler.class, "I");
        this.autoRelease = autoRelease;
    }

    
see SimpleChannelInboundHandler(Class, boolean) with true as boolean value. /**
     * see {@link #SimpleChannelInboundHandler(Class, boolean)} with {@code true} as boolean value.
     */
    protected SimpleChannelInboundHandler(Class<? extends I> inboundMessageType) {
        this(inboundMessageType, true);
    }

    
Create a new instance
Params:
inboundMessageType –    The type of messages to match
autoRelease –  true if handled messages should be released automatically by passing them to ReferenceCountUtil.release(Object)./**
     * Create a new instance
     *
     * @param inboundMessageType    The type of messages to match
     * @param autoRelease           {@code true} if handled messages should be released automatically by passing them to
     *                              {@link ReferenceCountUtil#release(Object)}.
     */
    protected SimpleChannelInboundHandler(Class<? extends I> inboundMessageType, boolean autoRelease) {
        matcher = TypeParameterMatcher.get(inboundMessageType);
        this.autoRelease = autoRelease;
    }

    
Returns true if the given message should be handled. If false it will be passed to the next ChannelInboundHandler in the ChannelPipeline. /**
     * Returns {@code true} if the given message should be handled. If {@code false} it will be passed to the next
     * {@link ChannelInboundHandler} in the {@link ChannelPipeline}.
     */
    public boolean acceptInboundMessage(Object msg) throws Exception {
        return matcher.match(msg);
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        boolean release = true;
        try {
            if (acceptInboundMessage(msg)) {
                @SuppressWarnings("unchecked")
                I imsg = (I) msg;
                channelRead0(ctx, imsg);
            } else {
                release = false;
                ctx.fireChannelRead(msg);
            }
        } finally {
            if (autoRelease && release) {
                ReferenceCountUtil.release(msg);
            }
        }
    }

    
Please keep in mind that this method will be renamed to messageReceived(ChannelHandlerContext, I) in 5.0. Is called for each message of type I. 
Params:
ctx –  the ChannelHandlerContext which this SimpleChannelInboundHandler belongs to
msg –           the message to handle
Throws:
Exception –    is thrown if an error occurred/**
     * <strong>Please keep in mind that this method will be renamed to
     * {@code messageReceived(ChannelHandlerContext, I)} in 5.0.</strong>
     *
     * Is called for each message of type {@link I}.
     *
     * @param ctx           the {@link ChannelHandlerContext} which this {@link SimpleChannelInboundHandler}
     *                      belongs to
     * @param msg           the message to handle
     * @throws Exception    is thrown if an error occurred
     */
    protected abstract void channelRead0(ChannelHandlerContext ctx, I msg) throws Exception;
}