Netty消息传递

1、消息如何在管道中流转 ，一个管道中会有多个handler,当前的一个handler如何往下面的一个handler传递一个对象

　　主要通过handler往下传递对象的方法是sendUpstream(event)

2、看下粘包和分包是怎么样一个情况
　　hello hello
　　通过定义一个稳定的结构 length + hello

1、为什么FrameDecoder return的对象就是往下传递的对象  （还是调用了sendUpstream）

2、buffer里面数据未被读取完怎么办？    （cumulation缓存）

3、为什么return null就可以缓存buffer     （cumulation缓存）

=============================分割线===========================

3、FrameDecoder里面的cumulation其实就是一个缓存的buffer对象

　　包头+长度+数据

　　把长度定义的很大，这种数据包，通常被称为socket攻击，字节流式攻击

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();
    }

}

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;

/**
 * 消息传递
 */
public class Server {

    public static void main(String[] args) {
        //服务类
        ServerBootstrap bootstrap = new ServerBootstrap();
        
        //boss线程监听端口，worker线程负责数据读写
        ExecutorService boss = Executors.newCachedThreadPool();
        ExecutorService worker = Executors.newCachedThreadPool();
        
        //设置niosocket工厂
        bootstrap.setFactory(new NioServerSocketChannelFactory(boss, worker));
        
        //设置管道的工厂
        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!!!");
    }

}

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);
        
        //传递给handler2
        ctx.sendUpstream(new UpstreamMessageEvent(ctx.getChannel(), "abc", e.getRemoteAddress()));
        ctx.sendUpstream(new UpstreamMessageEvent(ctx.getChannel(), "efg", e.getRemoteAddress()));
    }
}

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);
    }
}