Netty消息傳遞

知識點

1、消息如何在管道中流轉 ，一個管道中會有多個handler,當前的一個handler如何往下面的一個handler傳遞一個對象

　　主要通過handler往下傳遞對象的方法是sendUpstream(event)

2、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

1、為什么FrameDecoder return的對象就是往下傳遞的對象  （還是調用了sendUpstream）

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）

=============================分割線===========================

3、FrameDecoder里面的cumulation其實就是一個緩存的buffer對象

　　包頭+長度+數據

　　把長度定義的很大，這種數據包，通常被稱為socket攻擊，字節流式攻擊

1、Client.java

package com.example.netty.lesson11.pipeLine;

import java.net.Socket;

public class Client {

    public static void main(String[] args) throws Exception {

        Socket socket = new Socket("127.0.0.1", 51503);
        
        socket.getOutputStream().write("hello".getBytes());
        
        socket.close();
    }

}

2、Server.java

package com.example.netty.lesson11.pipeLine;

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

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;

/**
 * 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("handler1", new MyHandler1());
                pipeline.addLast("handler2", new MyHandler2());
                return pipeline;
            }
        });
        
        bootstrap.bind(new InetSocketAddress(51503));
        
        System.out.println("start!!!");
    }

}

3、MyHandler1.java

package com.example.netty.lesson11.pipeLine;

import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.SimpleChannelHandler;
import org.jboss.netty.channel.UpstreamMessageEvent;

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);
        System.out.println("handler1:" + message);
        
        //傳遞給handler2
        ctx.sendUpstream(new UpstreamMessageEvent(ctx.getChannel(), "abc", e.getRemoteAddress()));
        ctx.sendUpstream(new UpstreamMessageEvent(ctx.getChannel(), "efg", e.getRemoteAddress()));
    }
}

4、MyHandler2.java

package com.example.netty.lesson11.pipeLine;

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

public class MyHandler2 extends SimpleChannelHandler {

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

        String message = (String)e.getMessage();
        
        System.out.println("handler2:" + message);
    }
}

完畢！