Netty解決粘包問題

知識點

1、看下粘包和分包是怎么樣一個情況
　　hello hello
　　通過定義一個穩定的結構 length + hello

2、buffer里面數據未被讀取完怎么辦？    （cumulation緩存）

3、為什么return null就可以緩存buffer     （cumulation緩存）

1、Client.java

package com.example.netty.lesson11.packet;

import java.net.Socket;
import java.nio.ByteBuffer;

public class Client {

    public static void main(String[] args) throws Exception {
        /**
         * 會出現粘包現象,通過ByteBuffer解決粘包問題
         */
        Socket socket = new Socket("127.0.0.1", 51503);

        String message = "hello,ni hao ma?";
        byte[] bytes = message.getBytes();
        //4定義為包頭位數
        ByteBuffer buffer = ByteBuffer.allocate(4+bytes.length);
        buffer.putInt(bytes.length);
        buffer.put(bytes);

        byte[] array = buffer.array();
        for (int i = 0; i <1000 ; i++) {
            socket.getOutputStream().write(array);
        }

        socket.close();
    }

}

2、Server.java

package com.example.netty.lesson11.packet;

import com.example.netty.lesson11.pipeLine.MyHandler2;
import org.jboss.netty.bootstrap.ServerBootstrap;
import org.jboss.netty.channel.ChannelPipeline;
import org.jboss.netty.channel.ChannelPipelineFactory;
import org.jboss.netty.channel.Channels;
import org.jboss.netty.channel.socket.nio.NioServerSocketChannelFactory;

import java.net.InetSocketAddress;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * 消息傳遞
 */
public class Server {

    public static void main(String[] args) {
        //服務類
        ServerBootstrap bootstrap = new ServerBootstrap();
        
        //boss線程監聽端口，worker線程負責數據讀寫
        ExecutorService boss = Executors.newCachedThreadPool();
        ExecutorService worker = Executors.newCachedThreadPool();
        
        //設置niosocket工廠
        bootstrap.setFactory(new NioServerSocketChannelFactory(boss, worker));
        
        //設置管道的工廠
        bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
            
            @Override
            public ChannelPipeline getPipeline() throws Exception {

                ChannelPipeline pipeline = Channels.pipeline();
                pipeline.addLast("decoder", new MyDecoder());
                pipeline.addLast("handler1", new MyHandler1());
                return pipeline;
            }
        });
        
        bootstrap.bind(new InetSocketAddress(51503));
        
        System.out.println("start!!!");
    }

}

3、MyDecoder.java

package com.example.netty.lesson11.packet;

import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.frame.FrameDecoder;

/**
 * @author yangwj
 * @date 2020/4/6 10:48
 */
public class MyDecoder extends FrameDecoder {
    @Override
    protected Object decode(ChannelHandlerContext channelHandlerContext, Channel channel, ChannelBuffer buffer) throws Exception {
        if(buffer.readableBytes() >4){
            //標記
            buffer.markReaderIndex();
            //長度
            int length = buffer.readInt();
            if(buffer.readableBytes() < length){
                buffer.resetReaderIndex();
                //緩存當前剩余的buffer數據，等待剩下的數據到來
                return null;
            }
            //讀數據
            byte[] bytes = new byte[length];
            buffer.readBytes(bytes);
            //往下傳遞 ,和sendUpstream類似
            return  new String(bytes);
        }
        //緩存當前剩余的buffer數據，等待剩下的數據到來
        return null;
    }
}

4、MyHandler1.java

package com.example.netty.lesson11.packet;

import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.SimpleChannelHandler;

public class MyHandler1 extends SimpleChannelHandler {

    @Override
    public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {

//        ChannelBuffer buffer = (ChannelBuffer) e.getMessage();
//
//        byte[] array = buffer.array();
//        String message = new String(array);
        String message = (String) e.getMessage();
        System.out.println("handler1:" + message);

    }
}

完畢！