第一个简单netty程序

一个简单的netty的程序，主要是netty的客户端和服务端通信。

大部分说明都写在代码注释中

netty server

TimeServer

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;
 
public class TimeServer {
 
    public void bind(int port) throws Exception {
 
        // 配置 服务端的 NIO 线程组
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
 
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 1024)
                    .childHandler(new ChildChannelHandler());
 
            // 绑定端口，同步等待成功。
            ChannelFuture f = b.bind(port).sync();
            // 等待服务端监听端口关闭。
            f.channel().closeFuture().sync();
        } catch (Exception e) {
            // 退出，释放线程池资源
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
 
    private class ChildChannelHandler extends ChannelInitializer<SocketChannel> {
        @Override
        protected void initChannel(SocketChannel ch) throws Exception {
            ch.pipeline().addLast(new TimeServerHandler());
        }
    }
 
    public static void main(String[] args) throws Exception{
        int port = 8080;
        if (args != null && args.length > 0) {
            try {
                port = Integer.valueOf(args[0]);
            } catch (NumberFormatException e) {
            }
        }
        new TimeServer().bind(port);
    }
}

TimeServerHandler

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
 
import java.util.Date;
 
public class TimeServerHandler extends ChannelHandlerAdapter {
 
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf buf = (ByteBuf) msg;
        byte[] req = new byte[buf.readableBytes()];
        buf.readBytes(req);
        String body = new String(req,"UTF-8");
        System.out.println("the time server receive order : " + body);
        String currentTime = "QUERY TIME ORDER"
                .equalsIgnoreCase(body) ? new Date(
                System.currentTimeMillis()).toString()
                : "BAD ORDER";
        ByteBuf resp = Unpooled.copiedBuffer(currentTime.getBytes());
        ctx.write(resp);
    }
 
    /**
     * 当监听到端口时调用 channelActive 打印 "连接成功！"
     * @param ctx
     * @throws Exception
     */
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("连接成功！");
    }
 
    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
       ctx.flush();
    }
 
    /**
     * 当出现异常时，关闭连接
     */
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        System.out.println("出现异常，关闭");
        ctx.close();
    }
}

netty client

TimeClient

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 void connect(int port, String host) throws Exception {
 
        //配置客户端 NIO 线程组
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group).channel(NioSocketChannel.class)
                    .option(ChannelOption.TCP_NODELAY, true)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
 
                            ch.pipeline().addLast(new TimeClientHandler());
                        }
                    });
            // 发起异步连接操作
            ChannelFuture f = b.connect(host, port).sync();
            // 等待客户端链路关闭
            f.channel().closeFuture().sync();
        } finally {
            // 释放 NIO 线程组
            group.shutdownGracefully();
 
        }
    }
 
    public static void main(String[] args) throws Exception {
        int port = 8080;
 
        if (args != null && args.length > 0) {
            try {
                port = Integer.valueOf(args[0]);
            } catch (NumberFormatException e) {
            }
        }
        new TimeClient().connect(port, "127.0.0.1");
    }
}

TimeClientHandler

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
 
import java.util.logging.Logger;
 
public class TimeClientHandler extends ChannelHandlerAdapter {
 
    private static final Logger logger = Logger.getLogger(TimeClientHandler.class.getName());
 
    private final ByteBuf firstMessage;
 
    public TimeClientHandler() {
        byte[] req = "QUERY TIME ORDER".getBytes();
        firstMessage = Unpooled.buffer(req.length);
        firstMessage.writeBytes(req);
    }
 
    /**
     * 当连接成功时，调用 writeAndFlush 发送 firstMessage 到服务端
     * @param ctx
     * @throws Exception
     */
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        ctx.writeAndFlush(firstMessage);
    }
 
    /**
     * 当服务端的有数据发送过来时，调用 channelRead 接受数据，并打印
     * @param ctx
     * @param msg
     * @throws Exception
     */
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf buf = (ByteBuf) msg;
        byte[] req = new byte[buf.readableBytes()];
        buf.readBytes(req);
        String body = new String (req,"UTF-8");
        System.out.println("Now is : " + body);
    }
 
    /**
     * 出现异常时，打印错误，并关闭
     * @param ctx
     * @param cause
     * @throws Exception
     */
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        logger.warning("Unexpected  Exception  from downstream : " + cause.getMessage());
        ctx.close();
    }
}

个人感觉netty ,比java自带的NIO简单了很多，不过这只是一个简单小例子，后期可能会有更复杂的 。很期待后边的学习。