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/ 我下载的是最新版5.0.0

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)
								@Override
								public 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)
								@Override
								public 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：

</pre><pre name="code" class="java">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：