Java搭建简单Netty开发环境入门教程

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;

@Sharable
public 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;

@Sharable
public 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。

点击查看Netty结合Protobuf编解码

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