Netty权威指南之Netty入门应用

亦凉 2023-10-16 21:49 123阅读 0赞

本章节需要学习的内容如下：

1、Netty开发环境搭建

2、服务端程序开发NettyServer

3、客户端程序开发NettyClient

**第一节：Netty开发环境搭建**

（1）、访问Netty的官网[http://netty.io][http_netty.io],从【Download】标签页下载[netty-5.0.0.Alpha2.tar.bz2][]安装包，安装包不大，14.6M左右。下载完成后，如下截图:

![Center][]

(2)、通过解压缩工具打开压缩工具，如以下截图：

![Center 1][]

（3）、搭建Netty 应用工程，使用MyEclipse 10 创建普通的Java工程，同时创建Java源文件的package。

![Center 2][]

（4）、创建第三方类库存放文件夹lib,同时将netty-all-5.0.0.Alpha2.jar文件复制到lib目录下。

![Center 3][]

到此，Netty应用程序的开发环境已经搭建完毕。

**第二节：Netty服务端开发**

**温故知新：在开始使用Netty开发服务端之前，先回顾一下使用NIO进行服务端开发步骤：**

**1、创建ServerSocketChannle,并配置它为非阻塞模式。**

**2、绑定监听，配置TCP参数。比如blocklog大小。**

**3、创建一个独立的IO线程，用于轮训多路复用器Selector。**

**4、创建Selector,将之前创建的ServerSocketChannle注册到Selector上，监听SelectKey.Accept.**

**5、启动IO线程，在循环体中执行Selector.select()方法，轮训就绪的Channle.**

**6、当轮训到就绪状态的Channle,需要对其判断，如果是SelectorKey.Accept状态，说明是新客户端接入，则调用ServerSocketChannle.accept()的方法接受新的客户端。**

**7、设置新接入的客户端的链路SocketChannle为非阻塞模式，配置其他的TCP参数。**

**8、将SocketChannle注册到Selector,监听OP\_READ操作位。**

**9、如果轮训的Channle为OP\_READ,则说明SocketChannle中有新的就绪的数据包需要读取，构造ByteBuff对象，读取数据包。**

**10、如果轮训的Channle的状态为OP\_WRITE,说明还有数据没有发送完成，需要继续发送。**

**分析：一个简单的Java NIO服务端程序，如果我们选择使用Java JDK 的NIO库开发，竟然需要进过繁琐的十几步操作才能完成最基本的信息发送与接受，这也是我们选择Java NIO 开源框架的原因(Netty).**

**NettyServer.java**

package com.nio.server;
    
    import com.nio.handler.NettyServerHandler;
    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;
    
    
    
    /**
     * Created by vixuan-008 on 2015/6/19.
     */
    public class NettyServer {
        public static void main(String[] args)throws Exception{
            int port=17666;
            new NettyServer().bind(port);
    
    
        }
        public void bind(int port)throws Exception{
            //配置服务端的NIO线程池
            EventLoopGroup bossGroup=new NioEventLoopGroup();
            EventLoopGroup workGroup=new NioEventLoopGroup();
            try{
                ServerBootstrap b=new ServerBootstrap();
                b.group(bossGroup,workGroup).channel(NioServerSocketChannel.class).option(ChannelOption.SO_BACKLOG,1024).childHandler(new NettyServerHandler());
                //绑定端口，等待同步成功
                ChannelFuture f=b.bind(port).sync();
                //等待服务端关闭监听端口
                f.channel().closeFuture().sync();
    
            }finally {
                //释放线程池资源
                bossGroup.shutdownGracefully();
                workGroup.shutdownGracefully();
    
            }
    
    
        }
        //添加内部类
        private class ChildChannelHandler extends ChannelInitializer<SocketChannel>{
            @Override
            protected void initChannel(SocketChannel socketChannel) throws Exception {
                socketChannel.pipeline().addLast(new NettyServerHandler());
    
            }
        }
    
    }

NettyServerHandler.java

package com.nio.handler;
    
    import io.netty.buffer.ByteBuf;
    import io.netty.buffer.Unpooled;
    import io.netty.channel.ChannelHandlerAdapter;
    import io.netty.channel.ChannelHandlerContext;
    
    
    
    
    /**
     * Created by vixuan-008 on 2015/6/19.
     */
    public class NettyServerHandler extends ChannelHandlerAdapter {
        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
                ctx.close();
        }
    
        @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 server receiver data is:"+body);
            String currentTime="time".equalsIgnoreCase(body) ? new java.util.Date(System.currentTimeMillis()).toString():"no zuo no die";
            ByteBuf resp= Unpooled.copiedBuffer(currentTime.getBytes());
            ctx.write(resp);
        }
    
        @Override
        public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
            super.channelReadComplete(ctx);
            ctx.flush();
        }
    }

**第三节：Netty客户端开发**

NettyClient.java

package com.nio.client;
    
    import com.nio.handler.NettyClientHandler;
    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;
    
    
    
    
    /**
     * Created by vixuan-008 on 2015/6/19.
     */
    public class NettyClient {
        public static void main(String[] args)throws  Exception{
            int port=17666;
            new NettyClient().connect(port,"127.0.0.1");
    
        }
    
        public void connect(int port,String host)throws Exception{
            //配置客户端NIO线程池
            EventLoopGroup workGroup=new NioEventLoopGroup();
            try{
                io.netty.bootstrap.Bootstrap b=new io.netty.bootstrap.Bootstrap();
                b.group(workGroup).channel(NioSocketChannel.class).option(ChannelOption.TCP_NODELAY,true).handler(new ChannelInitializer<SocketChannel>() {
                    @Override
                    protected void initChannel(SocketChannel socketChannel) throws Exception {
                        socketChannel.pipeline().addLast(new NettyClientHandler());
                    }
                });
                //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
                workGroup.shutdownGracefully();
    
            }
        }
    
    
    }

NettyClientHandler.java

package com.nio.handler;
    
    import io.netty.buffer.ByteBuf;
    import io.netty.buffer.Unpooled;
    import io.netty.channel.ChannelHandlerAdapter;
    import io.netty.channel.ChannelHandlerContext;
    
    /**
     * Created by vixuan-008 on 2015/6/19.
     */
    public class NettyClientHandler extends ChannelHandlerAdapter {
        private final ByteBuf message;
    
        public NettyClientHandler() {
            byte[] req="time".getBytes();
            message= Unpooled.buffer(req.length);
            message.writeBytes(req);
        }
    
        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
    
            ctx.close();
        }
    
        @Override
        public void channelActive(ChannelHandlerContext ctx) throws Exception {
    
            ctx.writeAndFlush(message);
        }
    
        @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("this client receiver data is:"+body);
        }
    
        @Override
        public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
    
        }
    }

今天学习到此结束。

[http_netty.io]: http://netty.io
[netty-5.0.0.Alpha2.tar.bz2]: http://dl.bintray.com/netty/downloads/netty-5.0.0.Alpha2.tar.bz2
[Center]: https://img-blog.csdn.net/20150619025731390?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvemhvdXpoaXdlbmdhbmc=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center
[Center 1]: https://img-blog.csdn.net/20150619025859913?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvemhvdXpoaXdlbmdhbmc=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center
[Center 2]: https://img-blog.csdn.net/20150619105628936?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvemhvdXpoaXdlbmdhbmc=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center
[Center 3]: https://img-blog.csdn.net/20150619105855709?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvemhvdXpoaXdlbmdhbmc=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center