Netty之HelloWorld！

为什么要使用Netty？

Netty是一个基于NIO的简化版，使用Netty更方便使用Java进行异步操作。

传统的IO：

NIO：

从图上就可以看出来，NIO简化了不必要的线程连接，以往的Socket每多一个连接，都需要创建一个线程，这是一个额外的消耗，因此Java在1.4之后推出了NIO，用于简化线程操作。

NIO可以理解为New IO，也可以理解为Non-Blocking IO。

但由于NIO操作繁琐，而且API不易使用，因此Netty便应空而生，Netty是为了简化NIO而诞生的框架。

以下是一个Netty的HelloWorld示例：

Netty服务端：

package com.netty.server;

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;
import org.jboss.netty.handler.codec.string.StringDecoder;
import org.jboss.netty.handler.codec.string.StringEncoder;
/**
 * netty服务端入门
 * @author 小书包
 *
 */
public class Server {
	public static final int PORT = 10101;
	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 {
				//获得管道
				ChannelPipeline pipeline = Channels.pipeline();
				//字符串解码
				pipeline.addLast("decoder", new StringDecoder());
				//字符串编码
				pipeline.addLast("encoder", new StringEncoder());
				//具体的事件处理器
				pipeline.addLast("helloHandler", new HelloHandler());
				return pipeline;
			}
		});
		//绑定端口
		bootstrap.bind(new InetSocketAddress(PORT));
		
		System.out.println(" Server Start On " + PORT + "!!!");
		
	}

}

事件处理器

package com.netty.server;

import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.ChannelStateEvent;
import org.jboss.netty.channel.ExceptionEvent;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.SimpleChannelHandler;
/**
 * 消息接受处理类
 * @author 小书包
 *
 */
public class HelloHandler extends SimpleChannelHandler {

	/**
	 * 接收消息
	 */
	@Override
	public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
		String s = (String) e.getMessage();
		System.out.println(s);
		
		//回写数据
		ctx.getChannel().write("hi");
		super.messageReceived(ctx, e);
	}

	/**
	 * 捕获异常
	 */
	@Override
	public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) throws Exception {
		System.out.println("exceptionCaught");
		super.exceptionCaught(ctx, e);
	}

	/**
	 * 新连接
	 */
	@Override
	public void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
		System.out.println("channelConnected");
		super.channelConnected(ctx, e);
	}

	/**
	 * 必须是链接已经建立，关闭通道的时候才会触发
	 */
	@Override
	public void channelDisconnected(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
		System.out.println("channelDisconnected");
		super.channelDisconnected(ctx, e);
	}

	/**
	 * channel关闭的时候触发
	 */
	@Override
	public void channelClosed(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
		System.out.println("channelClosed");
		super.channelClosed(ctx, e);
	}
}

启动Server

Server Start On 10101!!!

使用Telnet进行连接

进入连接

channelConnected

输入send hello

服务端得到：

hello

并发送Hi到客户端

关闭Telnet

channelDisconnected
channelClosed

如果不使用Telent，使用Java代码进行连接

客户端代码

package com.netty.client;

import java.net.InetSocketAddress;
import java.util.Scanner;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import org.jboss.netty.bootstrap.ClientBootstrap;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelFuture;
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.handler.codec.string.StringDecoder;
import org.jboss.netty.handler.codec.string.StringEncoder;
/**
 * netty客户端入门
 * @author 小书包
 *
 */
public class Client {

	public static void main(String[] args) {
		
		//服务类
		ClientBootstrap bootstrap = new  ClientBootstrap();
		
		//线程池
		ExecutorService boss = Executors.newCachedThreadPool();
		ExecutorService worker = Executors.newCachedThreadPool();
		
		//socket工厂
		bootstrap.setFactory(new NioClientSocketChannelFactory(boss, worker));
		
		//管道工厂
		bootstrap.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("hiHandler", new HiHandler());
				return pipeline;
			}
		});
		
		//连接服务端
		ChannelFuture connect = bootstrap.connect(new InetSocketAddress("127.0.0.1", 10101));
		Channel channel = connect.getChannel();
		
		System.out.println("client start");
		
		Scanner scanner = new Scanner(System.in);
		while(true){
			System.out.println("请输入");
			channel.write(scanner.next());
		}
	}

}

事件处理器

package com.netty.client;

import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.ChannelStateEvent;
import org.jboss.netty.channel.ExceptionEvent;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.SimpleChannelHandler;
/**
 * 消息接受处理类
 * @author 小书包
 *
 */
public class HiHandler extends SimpleChannelHandler {

	/**
	 * 接收消息
	 */
	@Override
	public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {

		
		String s = (String) e.getMessage();
		System.out.println(s);
		
		super.messageReceived(ctx, e);
	}

	/**
	 * 捕获异常
	 */
	@Override
	public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) throws Exception {
		System.out.println("exceptionCaught");
		super.exceptionCaught(ctx, e);
	}

	/**
	 * 新连接
	 */
	@Override
	public void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
		System.out.println("channelConnected");
		super.channelConnected(ctx, e);
	}

	/**
	 * 必须是链接已经建立，关闭通道的时候才会触发
	 */
	@Override
	public void channelDisconnected(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
		System.out.println("channelDisconnected");
		super.channelDisconnected(ctx, e);
	}

	/**
	 * channel关闭的时候触发
	 */
	@Override
	public void channelClosed(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
		System.out.println("channelClosed");
		super.channelClosed(ctx, e);
	}
}

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