Java NIO框架Netty简单使用

转载请注明出处：http://blog.csdn.net/anxpp/article/details/52108238，谢谢！

    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() {
                 @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() {
                @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

1. package com.anxpp.io.utils;
2. import javax.script.ScriptEngine;
3. import javax.script.ScriptEngineManager;
4. import javax.script.ScriptException;
5. public enum Calculator {
6. Instance;
7. private final static ScriptEngine jse = new ScriptEngineManager().getEngineByName("JavaScript");
8. public Object cal(String expression) throws ScriptException{
9. return jse.eval(expression);
10. }
11. }

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. 1+5+5+5+5+5
2. 客户端发送消息：1+5+5+5+5+5
3. 服务器消息：26
4. 156158*458918+125615
5. 客户端发送消息：156158*458918+125615
6. 服务器消息：7.1663842659E10
7. 1895612+555+5+5+5+5+5+5+5-5*4/4
8. 客户端发送消息：1895612+555+5+5+5+5+5+5+5-5*4/4
9. 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：

1. 服务器开启：9090
2. 收到客户端消息:1+5+5+5+5+5
3. 收到客户端消息:156158*458918+125615
4. 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。