搭建简单的Netty开发环境

今天准备学学声明显赫的Netty框架，自然要先学会怎么搭建一个简单的Netty开发环境啦。话不多说，下面进入正文。

编辑器方面自然是推荐IntelJ idea了，idea的强大不必多说，百度一下你就知道。哈哈

下面就是准备Netty的jar包了，如果你会maven的话自然是使用maven最为方便了。只需要在pom文件中导入以下几行

<!-- https://mvnrepository.com/artifact/io.netty/netty-all -->    <dependency>      <groupId>io.netty</groupId>      <artifactId>netty-all</artifactId>      <version>4.1.16.Final</version>    </dependency>

当然啦，不会maven的也不用愁，可以在官网直接下载jar包，点击跳转。并在编辑器中将下载的jar包引入你的lib中，就可以愉快的开始Netty开发了

下面贴一个简单的netty案例

一、 服务端代码

1. EchoServerHandler.java

import io.netty.buffer.ByteBuf;import io.netty.buffer.Unpooled;import io.netty.channel.ChannelFutureListener;import io.netty.channel.ChannelHandler.Sharable;import io.netty.channel.ChannelHandlerContext;import io.netty.channel.ChannelInboundHandlerAdapter;import io.netty.util.CharsetUtil;@Sharablepublic class EchoServerHandler extends ChannelInboundHandlerAdapter{    @Override    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {        //将客户端传入的消息转换为Netty的ByteBuf类型        ByteBuf in = (ByteBuf) msg;        // 在控制台打印传入的消息        System.out.println(                "Server received: " + in.toString(CharsetUtil.UTF_8)        );        //将接收到的消息写给发送者，而不冲刷出站消息        ctx.write(in);    }    @Override    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {        // 将未处决消息冲刷到远程节点， 并且关闭该Channel        ctx.writeAndFlush(Unpooled.EMPTY_BUFFER)                .addListener(ChannelFutureListener.CLOSE);    }    /**     * 异常处理     * @param ctx     * @param cause     * @throws Exception     */    @Override    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {        //打印异常栈跟踪        cause.printStackTrace();        // 关闭该Channel        ctx.close();    }}

2. EchoServer.java

import io.netty.bootstrap.ServerBootstrap;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.NioServerSocketChannel;import java.net.InetSocketAddress;public class EchoServer {    private final static int port = 8080;    public static void main(String[] args) {        start();    }    private static void start() {        final EchoServerHandler serverHandler = new EchoServerHandler();        // 创建EventLoopGroup        EventLoopGroup bossGroup = new NioEventLoopGroup();        EventLoopGroup workerGroup = new NioEventLoopGroup();        // 创建EventLoopGroup        ServerBootstrap b = new ServerBootstrap();        b.group(bossGroup, workerGroup)                //指定所使用的NIO传输Channel        .channel(NioServerSocketChannel.class)                //使用指定的端口设置套接字地址        .localAddress(new InetSocketAddress(port))                // 添加一个EchoServerHandler到Channle的ChannelPipeline        .childHandler(new ChannelInitializer<SocketChannel>() {            @Override            protected void initChannel(SocketChannel socketChannel) throws Exception {                //EchoServerHandler被标注为@shareable,所以我们可以总是使用同样的案例                socketChannel.pipeline().addLast(serverHandler);            }        });        try {            // 异步地绑定服务器;调用sync方法阻塞等待直到绑定完成            ChannelFuture f = b.bind().sync();            // 获取Channel的CloseFuture，并且阻塞当前线程直到它完成            f.channel().closeFuture().sync();        } catch (InterruptedException e) {            e.printStackTrace();        } finally {            // 优雅的关闭EventLoopGroup，释放所有的资源            bossGroup.shutdownGracefully();            workerGroup.shutdownGracefully();        }    }}

二、 客户端代码

1. EchoClientHandler.java

import io.netty.buffer.ByteBuf;import io.netty.buffer.Unpooled;import io.netty.channel.ChannelHandler.Sharable;import io.netty.channel.ChannelHandlerContext;import io.netty.channel.SimpleChannelInboundHandler;import io.netty.util.CharsetUtil;@Sharablepublic class EchoClientHandler extends SimpleChannelInboundHandler<ByteBuf> {    @Override    public void channelActive(ChannelHandlerContext ctx) throws Exception {        //当被通知Channel是活跃的时候，发送一条消息        ctx.writeAndFlush(Unpooled.copiedBuffer("Netty rocks!", CharsetUtil.UTF_8));    }    @Override    protected void channelRead0(ChannelHandlerContext channelHandlerContext, ByteBuf byteBuf) throws Exception {        System.out.println(                "Client received: " + byteBuf.toString(CharsetUtil.UTF_8)        );    }    @Override    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {        cause.printStackTrace();        ctx.close();    }}

2. EchoClient.java

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;import java.net.InetSocketAddress;public class EchoClient {    private final static String HOST = "localhost";    private final static int PORT = 8080;    public static void start() {        EventLoopGroup group = new NioEventLoopGroup();        Bootstrap bootstrap = new Bootstrap();        bootstrap.group(group)                .channel(NioSocketChannel.class)                .remoteAddress(new InetSocketAddress(HOST, PORT))                .handler(new ChannelInitializer<SocketChannel>() {                    @Override                    protected void initChannel(SocketChannel socketChannel) throws Exception {                        socketChannel.pipeline().addLast(new EchoClientHandler());                    }                });        try {            ChannelFuture f = bootstrap.connect().sync();            f.channel().closeFuture().sync();        } catch (InterruptedException e) {            e.printStackTrace();        }finally {            group.shutdownGracefully();        }    }    public static void main(String[] args) {        start();    }}

先后运行EchoServer.java和EchoClient.java.

如果控制台分别打印了

Server received: Netty rocks!

和

Client received: Netty rocks!

那么恭喜你，你已经可以开始netty的开发了。