1.Netty入门

Netty入门

1.Netty介绍

（1）百度百科介绍：

Netty是由JBOSS提供的一个java开源框架。Netty提供异步的、事件驱动的网络应用程序框架和工具，用以快速开发高性能、高可靠性的网络服务器和客户端程序。

也就是说，Netty 是一个基于NIO的客户、服务器端编程框架，使用Netty 可以确保你快速和简单的开发出一个网络应用，例如实现了某种协议的客户、服务端应用。Netty相当于简化和流线化了网络应用的编程开发过程，例如：基于TCP和UDP的socket服务开发。

“快速”和“简单”并不用产生维护性或性能上的问题。Netty 是一个吸收了多种协议（包括FTP、SMTP、HTTP等各种二进制文本协议）的实现经验，并经过相当精心设计的项目。最终，Netty 成功的找到了一种方式，在保证易于开发的同时还保证了其应用的性能，稳定性和伸缩性。

（2）官网介绍：netty.io

Netty is an asynchronous event-driven network application framework

for rapid development of maintainable high performance protocol servers & clients.

（3）参考资料：

1. 参考书籍：Netty实战（Norman Maurer & Marvin Allen Wolfthal）
2. 参考官方文档：https://netty.io/wiki/user-guide.html
3. 参考网址：https://ifeve.com/tag/netty/

2.程序功能概述

客户端向服务器发送HelloNetty-Server!服务器向客户端返回Hello Netty-Client!

3.程序实现

1. 服务端ChannelHandler

   package com.xm.netty;
   
   import io.netty.buffer.ByteBuf;
   import io.netty.buffer.Unpooled;
   import io.netty.channel.ChannelFutureListener;
   import io.netty.channel.ChannelHandlerContext;
   import io.netty.channel.ChannelInboundHandlerAdapter;
   import io.netty.util.CharsetUtil;
   
   public class ServerHandler extends ChannelInboundHandlerAdapter {
   
   	@Override
   	public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
   		ByteBuf in = (ByteBuf) msg;
   		System.out.println("服务器接收："+in.toString(CharsetUtil.UTF_8));
   		in.clear();
   		String str = "Hello Netty-Client!";
   		in.writeBytes(str.getBytes());
   		ctx.write(in);
   	}
   
   	@Override
   	public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
   		ctx.writeAndFlush(Unpooled.EMPTY_BUFFER).addListener(ChannelFutureListener.CLOSE);
   	}	
   
   	@Override
   	public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
   		cause.printStackTrace();
   		ctx.close();
   	}
   
   }
   
   

2. 服务端Server

   package com.xm.netty;
   
   import java.net.InetSocketAddress;
   
   import io.netty.bootstrap.ServerBootstrap;
   import io.netty.channel.Channel;
   import io.netty.channel.ChannelFuture;
   import io.netty.channel.ChannelInitializer;
   import io.netty.channel.EventLoopGroup;
   import io.netty.channel.nio.NioEventLoopGroup;
   import io.netty.channel.socket.nio.NioServerSocketChannel;
   
   public class Server {
   
   	private final int port;
   
   	public Server(int port) {
   		this.port = port;
   	}
   
   	public static void main(String[] args) {
   		int port = 8989;
   		try {
   			new Server(port).start();
   		} catch (InterruptedException e) {
   			// TODO Auto-generated catch block
   			e.printStackTrace();
   		}
   	}
   
   	private void start() throws InterruptedException {
   		 final ServerHandler serverHandler = new ServerHandler();
   		 EventLoopGroup group = new NioEventLoopGroup();
   		 try {
   			ServerBootstrap bootstrap = new ServerBootstrap();
   			 bootstrap
   			 		.group(group)
   			 		.channel(NioServerSocketChannel.class)
   			 		.localAddress(new InetSocketAddress( port))
   			 		.childHandler(new ChannelInitializer() {
   			 			@Override
   			 			protected void initChannel(Channel ch) throws Exception {
   			 				ch.pipeline().addLast(serverHandler);
   			 			}
   					});
   			 ChannelFuture future = bootstrap.bind().sync();
   			 future.channel().closeFuture().sync();
   		} finally {
   			group.shutdownGracefully().sync();
   		}
   
   	}
   
   }
   
   

3. 客户端ChannelHandler

   package com.xm.netty;
   
   import io.netty.buffer.ByteBuf;
   import io.netty.buffer.Unpooled;
   import io.netty.channel.ChannelHandlerContext;
   import io.netty.channel.SimpleChannelInboundHandler;
   import io.netty.util.CharsetUtil;
   
   public class ClientHandler extends SimpleChannelInboundHandler<ByteBuf> {
   
   	@Override
   	public void channelActive(ChannelHandlerContext ctx) throws Exception {
   		ctx.writeAndFlush(Unpooled.copiedBuffer("Hello Netty-Server!",CharsetUtil.UTF_8));
   	}
   
   	@Override
   	protected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {
   		System.out.println("客户端接收到消息："+msg.toString(CharsetUtil.UTF_8));
   	}
   
   	@Override
   	public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
   		cause.printStackTrace();
   		ctx.close();
   	}
   
   }
   
   

4. 客户端Client

   package com.xm.netty;
   
   import io.netty.bootstrap.Bootstrap;
   import io.netty.channel.ChannelFuture;
   import io.netty.channel.ChannelInitializer;
   import io.netty.channel.EventLoopGroup;
   import io.netty.channel.nio.NioEventLoopGroup;
   import io.netty.channel.socket.SocketChannel;
   import io.netty.channel.socket.nio.NioSocketChannel;
   
   public class Client {
   
   	private final int port;
   	private final String host;
   
   	public Client(int port, String host) {
   		this.port = port;
   		this.host = host;
   	}
   
   	public static void main(String[] args) {
   
   		String host = "127.0.0.1";
   		int port = 8989;
   		try {
   			new Client(port, host).start();
   		} catch (InterruptedException e) {
   			// TODO Auto-generated catch block
   			e.printStackTrace();
   		}
   
   	}
   
   	private void start() throws InterruptedException {
   		EventLoopGroup group = new NioEventLoopGroup();
   		try {
   			Bootstrap bootstrap = new Bootstrap();
   			bootstrap
   					.group(group)
   					.channel(NioSocketChannel.class)
   					.remoteAddress(host, port)
   					.handler(new ChannelInitializer<SocketChannel>() {
   
   						@Override
   						protected void initChannel(SocketChannel ch) throws Exception {
   							ch.pipeline().addLast(new ClientHandler());
   						}
   
   					});
   
   			ChannelFuture future = bootstrap.connect().sync();
   			future.channel().closeFuture().sync();
   		} finally {
   			group.shutdownGracefully().sync();
   		}
   
   	}
   
   }
   
   

5. 导入依赖

   <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
     <groupId>com.xm</groupId>
     <artifactId>netty</artifactId>
     <version>0.0.1-SNAPSHOT</version>
   
     <dependencies>
   
   <dependency>
       <groupId>io.netty</groupId>
       <artifactId>netty-all</artifactId>
       <version>4.1.16.Final</version>
   </dependency>
   
     </dependencies>
   </project>
   

4.运行结果：

1. 服务端：

   服务器接收：Hello Netty-Server!

2. 客户端：

   客户端接收到消息：Hello Netty-Client!