Netty快速入门

最新推荐文章于 2024-12-06 19:51:00 发布

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什么是Netty

Netty 是一个基于 JAVA NIO 类库的异步通信框架，它的架构特点是：异步非阻塞、基于事件驱动、高性能、高可靠性和高可定制性。

Netty应用场景

1.分布式开源框架中dubbo、Zookeeper，RocketMQ底层rpc通讯使用就是netty（底层nio），底层协议都是用的tcp或udp协议。

2.游戏开发中，底层使用netty通讯。

为什么选择netty

在本小节，我们总结下为什么不建议开发者直接使用JDK的NIO类库进行开发的原因：

1) NIO的类库和API繁杂，使用麻烦，你需要熟练掌握Selector、ServerSocketChannel、SocketChannel、ByteBuffer等；

2) 需要具备其它的额外技能做铺垫，例如熟悉Java多线程编程，因为NIO编程涉及到Reactor模式，你必须对多线程和网路编程非常熟悉，才能编写出高质量的NIO程序；

3) 可靠性能力补齐，工作量和难度都非常大。例如客户端面临断连重连、网络闪断、半包读写、失败缓存、网络拥塞和异常码流的处理等等，NIO编程的特点是功能开发相对容易，但是可靠性能力补齐工作量和难度都非常大；

4) JDK NIO的BUG，例如臭名昭著的epoll bug，它会导致Selector空轮询，最终导致CPU 100%。官方声称在JDK1.6版本的update18修复了该问题，但是直到JDK1.7版本该问题仍旧存在，只不过该bug发生概率降低了一些而已，它并没有被根本解决。

package com.jinglitong.shop.controller;

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.ChannelHandlerContext;
import org.jboss.netty.channel.ChannelPipeline;
import org.jboss.netty.channel.ChannelPipelineFactory;
import org.jboss.netty.channel.ChannelStateEvent;
import org.jboss.netty.channel.Channels;
import org.jboss.netty.channel.ExceptionEvent;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.SimpleChannelHandler;
import org.jboss.netty.channel.socket.nio.NioServerSocketChannelFactory;
import org.jboss.netty.handler.codec.string.StringDecoder;
import org.jboss.netty.handler.codec.string.StringEncoder;

class ServerHandler extends SimpleChannelHandler {

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

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

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

	}

	/**
	 * 接受消息
	 */
	public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
		super.messageReceived(ctx, e);
//		System.out.println("messageReceived");
		System.out.println("服务器端收到客户端消息:"+e.getMessage());
		//回复内容
		ctx.getChannel().write("好的");
	}

}
// netty 服务器端
public class NettyServer {

	public static void main(String[] args) {
		// 创建服务类对象
		ServerBootstrap serverBootstrap = new ServerBootstrap();
		// 创建两个线程池 分别为监听监听端口 ，nio监听
		ExecutorService boos = Executors.newCachedThreadPool();
		ExecutorService worker = Executors.newCachedThreadPool();
		// 设置工程 并把两个线程池加入中
		serverBootstrap.setFactory(new NioServerSocketChannelFactory(boos, worker));
		// 设置管道工厂
		serverBootstrap.setPipelineFactory(new ChannelPipelineFactory() {

			public ChannelPipeline getPipeline() throws Exception {
				ChannelPipeline pipeline = Channels.pipeline();
				//将数据转换为string类型.
				pipeline.addLast("decoder", new StringDecoder());
				pipeline.addLast("encoder", new StringEncoder());
				pipeline.addLast("serverHandler", new ServerHandler());
				return pipeline;
			}
		});
		// 绑定端口号
		serverBootstrap.bind(new InetSocketAddress(9090));
		System.out.println("netty server启动....");
	}


}


package com.jinglitong.shop.controller;

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.ChannelHandlerContext;
import org.jboss.netty.channel.ChannelPipeline;
import org.jboss.netty.channel.ChannelPipelineFactory;
import org.jboss.netty.channel.ChannelStateEvent;
import org.jboss.netty.channel.Channels;
import org.jboss.netty.channel.ExceptionEvent;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.SimpleChannelHandler;
import org.jboss.netty.channel.socket.nio.NioClientSocketChannelFactory;
import org.jboss.netty.handler.codec.string.StringDecoder;
import org.jboss.netty.handler.codec.string.StringEncoder;
class ClientHandler extends SimpleChannelHandler {

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

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

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

	}

	/**
	 * 接受消息
	 */
	public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
		super.messageReceived(ctx, e);
//		System.out.println("messageReceived");
		System.out.println("服务器端向客户端回复内容:"+e.getMessage());
		//回复内容
//		ctx.getChannel().write("好的");
	}

}
public class NettyClient {

	public static void main(String[] args) {
		System.out.println("netty client启动...");
		// 创建客户端类
		ClientBootstrap clientBootstrap = new ClientBootstrap();
		// 线程池
		ExecutorService boos = Executors.newCachedThreadPool();
		ExecutorService worker = Executors.newCachedThreadPool();
		clientBootstrap.setFactory(new NioClientSocketChannelFactory(boos, worker));
		clientBootstrap.setPipelineFactory(new ChannelPipelineFactory() {

			public ChannelPipeline getPipeline() throws Exception {
				ChannelPipeline pipeline = Channels.pipeline();
				// 将数据转换为string类型.
				pipeline.addLast("decoder", new StringDecoder());
				pipeline.addLast("encoder", new StringEncoder());
				pipeline.addLast("clientHandler", new ClientHandler());
				return pipeline;

			}
		});
		//连接服务端
		ChannelFuture connect = clientBootstrap.connect(new InetSocketAddress("127.0.0.1", 9090));
		Channel channel = connect.getChannel();
		System.out.println("client start");
		Scanner scanner=	new Scanner(System.in);
		while (true) {
			System.out.println("请输输入内容...");
			channel.write(scanner.next());
		}
	}
}