com.alibaba.tmq.common.remoting.netty.NettyDecoder Maven / Gradle / Ivy

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/**
 * Copyright (C) 2010-2013 Alibaba Group Holding Limited
 *
 * 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 com.alibaba.tmq.common.remoting.netty;

import java.nio.ByteBuffer;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.alibaba.tmq.common.helper.RemotingHelper;
import com.alibaba.tmq.common.remoting.protocol.RemotingCommand;
import com.alibaba.tmq.common.util.RemotingUtil;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.LengthFieldBasedFrameDecoder;


/**
 * 协议解码器
 *
 * @author shijia.wxr
 * @since 2013-7-13
 */
public class NettyDecoder extends LengthFieldBasedFrameDecoder {

    private static final Log log = LogFactory.getLog(NettyDecoder.class);

    private static final int FRAME_MAX_LENGTH = Integer.MAX_VALUE;


    public NettyDecoder() {
        super(FRAME_MAX_LENGTH, 0, 4, 0, 4);
    }


    @Override
    public Object decode(ChannelHandlerContext ctx, ByteBuf in) throws Exception {
        ByteBuf frame = null;
        try {
            frame = (ByteBuf) super.decode(ctx, in);
            if (null == frame) {
                return null;
            }

            ByteBuffer byteBuffer = frame.nioBuffer();

            return RemotingCommand.decode(byteBuffer);
        }
        catch (Throwable e) {
            log.error("decode exception, " + RemotingHelper.parseChannelRemoteAddr(ctx.channel()), e);
            // 这里关闭后， 会在pipeline中产生事件，通过具体的close事件来清理数据结构
            RemotingUtil.closeChannel(ctx.channel());
        }
        finally {
            if (null != frame) {
                frame.release();
            }
        }

        return null;
    }
}