Netty学习笔记一 项目demo

Netty是一个由JBoss提供的异步的，事件驱动的网络应用程序框架工具，用来开发高性能 高可靠性的网络服务器和客户端程序。

Netty 是一个基于NIO的客户/服务端编程框架，可以简化网络应用的编程开发过程。

这是官网上的结构图：

在线文档地址：http://netty.io/5.0/api/index.html

中文guide：http://ifeve.com/netty5-user-guide

一、java下Netty学习

1.下载 http://netty.io/  据说5.0版本被废弃了，现在我下载的是4.1.6

2.代码学习

二、Discard丢弃服务：

1.新建 java项目，把下载的文件解压，把jar/all-in-one放到项目里，并加到BuildPath

2.把官方测试代码运行起来：

package io.netty.example.discard;import io.netty.buffer.ByteBuf;import io.netty.channel.ChannelHandlerContext;import io.netty.channel.ChannelHandlerAdapter;/** * Handles a server-side channel. */public class DiscardServerHandler extends ChannelHandlerAdapter { // (1)    @Override    public void channelRead(ChannelHandlerContext ctx, Object msg) { // (2)        // Discard the received data silently.        ((ByteBuf) msg).release(); // (3)    }    @Override    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) { // (4)        // Close the connection when an exception is raised.        cause.printStackTrace();        ctx.close();    }}

package io.netty.example.discard;import io.netty.bootstrap.ServerBootstrap;import io.netty.channel.ChannelFuture;import io.netty.channel.ChannelInitializer;import io.netty.channel.ChannelOption;import io.netty.channel.EventLoopGroup;import io.netty.channel.nio.NioEventLoopGroup;import io.netty.channel.socket.SocketChannel;import io.netty.channel.socket.nio.NioServerSocketChannel;/** * Discards any incoming data. */public class DiscardServer {private int port;public DiscardServer(int port) {this.port = port;}public void run() throws Exception {EventLoopGroup bossGroup = new NioEventLoopGroup(); // (1)EventLoopGroup workerGroup = new NioEventLoopGroup();try {ServerBootstrap b = new ServerBootstrap(); // (2)b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class) // (3).childHandler(new ChannelInitializer<SocketChannel>() { // (4)@Overridepublic void initChannel(SocketChannel ch)throws Exception {ch.pipeline().addLast(new DiscardServerHandler());}}).option(ChannelOption.SO_BACKLOG, 128) // (5).childOption(ChannelOption.SO_KEEPALIVE, true); // (6)// Bind and start to accept incoming connections.ChannelFuture f = b.bind(port).sync(); // (7)// Wait until the server socket is closed.// In this example, this does not happen, but you can do that to// gracefully// shut down your server.f.channel().closeFuture().sync();} finally {workerGroup.shutdownGracefully();bossGroup.shutdownGracefully();}}public static void main(String[] args) throws Exception {int port;if (args.length > 0) {port = Integer.parseInt(args[0]);} else {port = 8080;}new DiscardServer(port).run();}}

设下断点，debug运行：

启动PuTTY，连接本机8080端口，Connection type:选择Telnet，

Telnet连接时，和发送字符时，程序会停在16行位置。

修改channelRead函数：

    @Override    public void channelRead(ChannelHandlerContext ctx, Object msg) { // (2)        // Discard the received data silently.        ctx.write(msg);        ctx.flush();    }

再次运行，现在telnet发送数据后，会回显出来。

TIME服务

添加类：

package io.netty.example.time;import io.netty.buffer.ByteBuf;import io.netty.channel.ChannelFuture;import io.netty.channel.ChannelFutureListener;import io.netty.channel.ChannelHandlerAdapter;import io.netty.channel.ChannelHandlerContext;public class TimeServerHandler extends ChannelHandlerAdapter {    @Override    public void channelActive(final ChannelHandlerContext ctx) { // (1)        final ByteBuf time = ctx.alloc().buffer(4); // (2)        time.writeInt((int) (System.currentTimeMillis() / 1000L + 2208988800L));        final ChannelFuture f = ctx.writeAndFlush(time); // (3)        f.addListener(new ChannelFutureListener() {            @Override            public void operationComplete(ChannelFuture future) {                assert f == future;                ctx.close();            }        }); // (4)    }    @Override    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {        cause.printStackTrace();        ctx.close();    }}

修改DiscardServer

package io.netty.example.discard;import io.netty.bootstrap.ServerBootstrap;import io.netty.channel.ChannelFuture;import io.netty.channel.ChannelInitializer;import io.netty.channel.ChannelOption;import io.netty.channel.EventLoopGroup;import io.netty.channel.nio.NioEventLoopGroup;import io.netty.channel.socket.SocketChannel;import io.netty.channel.socket.nio.NioServerSocketChannel;import io.netty.example.time.TimeServerHandler;/** * Discards any incoming data. */public class DiscardServer {private int port;public DiscardServer(int port) {this.port = port;}public void run() throws Exception {EventLoopGroup bossGroup = new NioEventLoopGroup(); // (1)EventLoopGroup workerGroup = new NioEventLoopGroup();try {ServerBootstrap b = new ServerBootstrap(); // (2)b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class) // (3).childHandler(new ChannelInitializer<SocketChannel>() { // (4)@Overridepublic void initChannel(SocketChannel ch)throws Exception {ch.pipeline().addLast(new TimeServerHandler());}}).option(ChannelOption.SO_BACKLOG, 128) // (5).childOption(ChannelOption.SO_KEEPALIVE, true); // (6)// Bind and start to accept incoming connections.ChannelFuture f = b.bind(port).sync(); // (7)// Wait until the server socket is closed.// In this example, this does not happen, but you can do that to// gracefully// shut down your server.f.channel().closeFuture().sync();} finally {workerGroup.shutdownGracefully();bossGroup.shutdownGracefully();}}public static void main(String[] args) throws Exception {int port;if (args.length > 0) {port = Integer.parseInt(args[0]);} else {port = 8080;}new DiscardServer(port).run();}}

在Ubuntu下安装rdate后测试：

Time客户端

另建一个项目：

package io.netty.example.time;import io.netty.bootstrap.Bootstrap;import io.netty.channel.ChannelFuture;import io.netty.channel.ChannelInitializer;import io.netty.channel.ChannelOption;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 TimeClient {    public static void main(String[] args) throws Exception {        String host = args[0];        int port = Integer.parseInt(args[1]);        EventLoopGroup workerGroup = new NioEventLoopGroup();        try {            Bootstrap b = new Bootstrap(); // (1)            b.group(workerGroup); // (2)            b.channel(NioSocketChannel.class); // (3)            b.option(ChannelOption.SO_KEEPALIVE, true); // (4)            b.handler(new ChannelInitializer<SocketChannel>() {                @Override                public void initChannel(SocketChannel ch) throws Exception {                    ch.pipeline().addLast(new TimeClientHandler());                }            });            // Start the client.            ChannelFuture f = b.connect(host, port).sync(); // (5)            // Wait until the connection is closed.            f.channel().closeFuture().sync();        } finally {            workerGroup.shutdownGracefully();        }    }}

package io.netty.example.time;import io.netty.buffer.ByteBuf;import io.netty.channel.ChannelHandlerAdapter;import io.netty.channel.ChannelHandlerContext;import java.util.Date;public class TimeClientHandler extends ChannelHandlerAdapter {    @Override    public void channelRead(ChannelHandlerContext ctx, Object msg) {        ByteBuf m = (ByteBuf) msg; // (1)        try {            long currentTimeMillis = (m.readUnsignedInt() - 2208988800L) * 1000L;            System.out.println(new Date(currentTimeMillis));            ctx.close();        } finally {            m.release();        }    }    @Override    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {        cause.printStackTrace();        ctx.close();    }}

运行结果：