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    之前写了一篇文章:Java 网络IO编程总结(BIO、NIO、AIO均含完整实例代码),介绍了如何使用Java原生IO支持进行网络编程,本文介绍一种更为简单的方式,即Java NIO框架。

    Netty是业界最流行的NIO框架之一,具有良好的健壮性、功能、性能、可定制性和可扩展性。同时,它提供的十分简单的API,大大简化了我们的网络编程。

    同Java IO介绍的文章一样,本文所展示的例子,实现了一个相同的功能。

1、服务端

    Server:

package com.anxpp.io.calculator.netty;
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 Server {
    private int port;
    public Server(int port) {
        this.port = port;
    }
    public void run() throws Exception {
        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)
             .childOption(ChannelOption.SO_KEEPALIVE, true)
             .childHandler(new ChannelInitializer<SocketChannel>() {
                 @Override
                 public void initChannel(SocketChannel ch) throws Exception {
                     ch.pipeline().addLast(new ServerHandler());
                 }
             });
            ChannelFuture f = b.bind(port).sync();
            System.out.println("服务器开启:"+port);
            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 = 9090;
        }
        new Server(port).run();
    }
}

    ServerHandler:

package com.anxpp.io.calculator.netty;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import java.io.UnsupportedEncodingException;
import com.anxpp.io.utils.Calculator;
public class ServerHandler extends ChannelInboundHandlerAdapter {
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws UnsupportedEncodingException {
        ByteBuf in = (ByteBuf) msg;
        byte[] req = new byte[in.readableBytes()];
        in.readBytes(req);
        String body = new String(req,"utf-8");
        System.out.println("收到客户端消息:"+body);
        String calrResult = null;
        try{
            calrResult = Calculator.Instance.cal(body).toString();
        }catch(Exception e){
            calrResult = "错误的表达式:" + e.getMessage();
        }
        ctx.write(Unpooled.copiedBuffer(calrResult.getBytes()));
    }
    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        ctx.flush();
    }
    /**
     * 异常处理
     */
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}

2、客户端

    Client:

package com.anxpp.io.calculator.netty;
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;
import java.util.Scanner;
public class Client implements Runnable{
    static ClientHandler client = new ClientHandler();
    public static void main(String[] args) throws Exception {
        new Thread(new Client()).start();
        @SuppressWarnings("resource")
        Scanner scanner = new Scanner(System.in);
        while(client.sendMsg(scanner.nextLine()));
    }
    @Override
    public void run() {
        String host = "127.0.0.1";
        int port = 9090;
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(workerGroup);
            b.channel(NioSocketChannel.class);
            b.option(ChannelOption.SO_KEEPALIVE, true);
            b.handler(new ChannelInitializer<SocketChannel>() {
                @Override
                public void initChannel(SocketChannel ch) throws Exception {
                    ch.pipeline().addLast(client);
                }
            });
            ChannelFuture f = b.connect(host, port).sync();
            f.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            workerGroup.shutdownGracefully();
        }
    }
}

    ClientHandler:

package com.anxpp.io.calculator.netty;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import java.io.UnsupportedEncodingException;
public class ClientHandler extends ChannelInboundHandlerAdapter {
    ChannelHandlerContext ctx;
    /**
     * tcp链路简历成功后调用
     */
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        this.ctx = ctx;
    }
    public boolean sendMsg(String msg){
        System.out.println("客户端发送消息:"+msg);
        byte[] req = msg.getBytes();
        ByteBuf m = Unpooled.buffer(req.length);
        m.writeBytes(req);
        ctx.writeAndFlush(m);
        return msg.equals("q")?false:true;
    }
    /**
     * 收到服务器消息后调用
     * @throws UnsupportedEncodingException 
     */
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws UnsupportedEncodingException {
        ByteBuf buf = (ByteBuf) msg;
        byte[] req = new byte[buf.readableBytes()];
        buf.readBytes(req);
        String body = new String(req,"utf-8");
        System.out.println("服务器消息:"+body);
    }
    /**
     * 发生异常时调用
     */
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}

3、用于计算的工具类

package com.anxpp.io.utils;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
public enum Calculator {
    Instance;
    private final static ScriptEngine jse = new ScriptEngineManager().getEngineByName("JavaScript");
    public Object cal(String expression) throws ScriptException{
        return jse.eval(expression);
    }
}

4、测试

    分别启动服务端和客户端,然后再客户端控制台输入表达式:

1+5+5+5+5+5
客户端发送消息:1+5+5+5+5+5
服务器消息:26
156158*458918+125615
客户端发送消息:156158*458918+125615
服务器消息:7.1663842659E10
1895612+555+5+5+5+5+5+5+5-5*4/4
客户端发送消息:1895612+555+5+5+5+5+5+5+5-5*4/4
服务器消息:1896197

    可以看到服务端返回的结果。

    查看服务端控制台:

服务器开启:9090
收到客户端消息:1+5+5+5+5+5
收到客户端消息:156158*458918+125615
收到客户端消息:1895612+555+5+5+5+5+5+5+5-5*4/4

5、更多

    相关文章:

    Java 网络IO编程总结(BIO、NIO、AIO均含完整实例代码)

    本文例子以及Java BIO NIO AIO例子的源码Git地址:https://github.com/anxpp/Java-IO.git

    后续会继续更新Netty相关内容,直到一个简陋的通讯服务器完成。