Netty框架

Netty框架：
Netty是一個基於JAVA NIO類庫的異步通訊框架，它的架構特點是異步非阻塞，基於事件驅動，高性能，高可靠性和高可定製性。
Netty應用場景：
1.分佈式開源框架dubbo，Zookeeper，RocketMQ底層rpc通訊使用就是netty。
2.遊戲開發中，底層是用netty通訊。
爲啥子選擇netty：
NIO的類庫和api繁雜，使用麻煩。需要熟悉掌握Selector，ServerSocketChannel SocketChannel ByteBuffer等；
需要具備其他額外的技能做鋪墊，多線程編程，因爲NIO編程涉及到Reactor模式，必須對多線程和網絡編程非常熟悉，才能寫出高質量的NIO程序。
可靠性能力補齊，工作量和難度非常大，例如客戶端面臨斷鏈重連，網絡閃斷，半包讀寫，失敗緩存，網絡擁塞和異常碼流的處理等等，NIO編程的特點即使功能開發相對容易，但是可靠性能力補齊工作量和難度非常大。
解決JDK的bug 。
Netty服務器端：

package com.itmayiedu.day04;



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.NioClientSocketChannelFactory;
import org.jboss.netty.channel.socket.nio.NioServerSocketChannelFactory;
import org.jboss.netty.handler.codec.string.StringDecoder;
import org.jboss.netty.handler.codec.string.StringEncoder;

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


/**
 * Netty服務器端
 */
public class NettyDem01 {
    public static void main(String[] args) {
        test01();
    }
    public static void test01(){
    //創建服務對象
       ServerBootstrap serverBootstrap =  new ServerBootstrap();
        //創建兩個線程池 一個監聽端口號 一個監聽NIO
        ExecutorService boos = Executors.newCachedThreadPool();
        ExecutorService work = Executors.newCachedThreadPool();
        //線程池放入到工程組中
        serverBootstrap.setFactory(new NioServerSocketChannelFactory(boos,work));
        //誰管道工程
        serverBootstrap.setPipelineFactory(new ChannelPipelineFactory() {
            //設置管道
            @Override
            public ChannelPipeline getPipeline() throws Exception {
                ChannelPipeline pipeline = Channels.pipeline();
                pipeline.addLast("decoder",new StringDecoder());
                pipeline.addLast("encoder",new StringEncoder());
                pipeline.addLast("serverHandler",new ServerHandler());
                return pipeline;
            }
        });
        //綁定端口號
        serverBootstrap.bind(new InetSocketAddress(8990));
        System.out.println("Netty服務端啓動");

        while (true){
            try{
                Thread.sleep(1000);
                System.out.println("每隔1秒打印一次");
            }catch (Exception ex){

            }
        }
    }
}

package com.itmayiedu.day04;

import org.jboss.netty.channel.*;

public class ServerHandler extends SimpleChannelHandler {
    //接受客戶端數據
    @Override
    public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
        super.messageReceived(ctx, e);
        System.out.println("================>>>>>>>>>+messageReceived");
        System.out.println("================>>>>>>>>服務端的數據："+e.getMessage());
    }
    //接受出現的異常
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) throws Exception {
        super.exceptionCaught(ctx, e);
    }
    //必須建立連接，關閉通道是纔會觸發
    @Override
    public void channelDisconnected(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
        super.channelDisconnected(ctx, e);
    }
    //通道別關閉的時候觸發
    @Override
    public void channelClosed(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
        super.channelClosed(ctx, e);
    }
}

Netty客戶端代碼：

package com.itmayiedu.day04;

import org.jboss.netty.bootstrap.ClientBootstrap;
import org.jboss.netty.channel.*;
import org.jboss.netty.channel.socket.nio.NioClientSocketChannelFactory;
import org.jboss.netty.handler.codec.string.StringDecoder;
import org.jboss.netty.handler.codec.string.StringEncoder;

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

/**
 * Netty 客戶端
 */
public class NettyClient {


    public static void main(String[] args) {
        ClientBootstrap clientBootstrap= new ClientBootstrap();
        ExecutorService book = Executors.newCachedThreadPool();
        ExecutorService wook = Executors.newCachedThreadPool();
        clientBootstrap.setFactory(new NioClientSocketChannelFactory(book,wook));
        clientBootstrap.setPipelineFactory(new ChannelPipelineFactory() {
            @Override
            public ChannelPipeline getPipeline() throws Exception {
                ChannelPipeline pipeline = Channels.pipeline();
                pipeline.addLast("decoder",new StringDecoder());
                pipeline.addLast("encoder",new StringEncoder());
                pipeline.addLast("clientHandler",new ClientHandler());
                return pipeline;
            }
        });
        //綁定端口號
        ChannelFuture connect = clientBootstrap.connect(new InetSocketAddress("127.0.0.1", 8990));
        System.out.println("====================>>>>>>>>>>客戶端已經啓動。。");
        Channel channel = connect.getChannel();
        Scanner scanner = new Scanner(System.in);
        while(true){
            System.out.println("===============>>>>>>>>>>>>>>請輸入內容");
            channel.write(scanner.next());

        }
    }
}

ClientHandler

package com.itmayiedu.day04;

import org.jboss.netty.channel.*;

public class ClientHandler extends SimpleChannelHandler {
    @Override
    public void channelClosed(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
        super.channelClosed(ctx, e);
    }

    @Override
    public void channelDisconnected(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
        super.channelDisconnected(ctx, e);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) throws Exception {
        super.exceptionCaught(ctx, e);
    }

    @Override
    public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
        super.messageReceived(ctx, e);
        System.out.println("=================>>>>>>>>:客戶端發送的數據："+e.getMessage());
        ctx.getChannel().write("你好啊");
    }
}

`` `
io和NIO區別：
	NIO面向緩衝區，非阻塞（是通過選擇器實現的）
	IO面向流，是阻塞的。