[转]Netty入门(最简单的Netty客户端/服务器程序)

　Java中的NIO是一种解决阻塞式IO问题的基本技术，但是NIO的编写对java程序员是有比较高的要求的。那么Netty就是一种简化操作的一个成熟的网络IO编程框架。这里简单介绍一个程序，代码是《netty in action》里面的，不过那个里面的实例有点问题，反正我没有跑成功，修改后成功。直接上代码：

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一、服务器编写

　　Server代码，监听连接

 1 package com.gerry.netty.server;
 2
 3 import io.netty.bootstrap.ServerBootstrap;
 4 import io.netty.channel.ChannelFuture;
 5 import io.netty.channel.ChannelInitializer;
 6 import io.netty.channel.EventLoopGroup;
 7 import io.netty.channel.nio.NioEventLoopGroup;
 8 import io.netty.channel.socket.SocketChannel;
 9 import io.netty.channel.socket.nio.NioServerSocketChannel;
10
11 public class EchoServer {
12     private final int port;
13
14     public EchoServer(int port) {
15         this.port = port;
16     }
17
18     public void start() throws Exception {
19         EventLoopGroup group = new NioEventLoopGroup();
20         try {
21             ServerBootstrap sb = new ServerBootstrap();
22             sb.group(group) // 绑定线程池
23                     .channel(NioServerSocketChannel.class) // 指定使用的channel
24                     .localAddress(this.port)// 绑定监听端口
25                     .childHandler(new ChannelInitializer<SocketChannel>() { // 绑定客户端连接时候触发操作
26
27                                 @Override
28                                 protected void initChannel(SocketChannel ch) throws Exception {
29                                     System.out.println("connected...; Client:" + ch.remoteAddress());
30                                     ch.pipeline().addLast(new EchoServerHandler()); // 客户端触发操作
31                                 }
32                             });
33             ChannelFuture cf = sb.bind().sync(); // 服务器异步创建绑定
34             System.out.println(EchoServer.class + " started and listen on " + cf.channel().localAddress());
35             cf.channel().closeFuture().sync(); // 关闭服务器通道
36         } finally {
37             group.shutdownGracefully().sync(); // 释放线程池资源
38         }
39     }
40
41     public static void main(String[] args) throws Exception {
42         new EchoServer(65535).start(); // 启动
43     }
44 }

　　具体的处理客户端连接的代码

 1 package com.gerry.netty.server;
 2
 3 import io.netty.buffer.Unpooled;
 4 import io.netty.channel.ChannelFutureListener;
 5 import io.netty.channel.ChannelHandlerContext;
 6 import io.netty.channel.ChannelInboundHandlerAdapter;
 7
 8 public class EchoServerHandler extends ChannelInboundHandlerAdapter {
 9     @Override
10     public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
11         System.out.println("server channelRead...; received:" + msg);
12         ctx.write(msg);
13     }
14
15     @Override
16     public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
17         System.out.println("server channelReadComplete..");
18         // 第一种方法：写一个空的buf，并刷新写出区域。完成后关闭sock channel连接。
19         ctx.writeAndFlush(Unpooled.EMPTY_BUFFER).addListener(ChannelFutureListener.CLOSE);
20         //ctx.flush(); // 第二种方法：在client端关闭channel连接，这样的话，会触发两次channelReadComplete方法。
21         //ctx.flush().close().sync(); // 第三种：改成这种写法也可以，但是这中写法，没有第一种方法的好。
22     }
23
24     @Override
25     public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
26         System.out.println("server occur exception:" + cause.getMessage());
27         cause.printStackTrace();
28         ctx.close(); // 关闭发生异常的连接
29     }
30 }

二、客户端编写

　　具体的连接代码

 1 package com.gerry.netty.client;
 2
 3 import io.netty.bootstrap.Bootstrap;
 4 import io.netty.channel.ChannelFuture;
 5 import io.netty.channel.ChannelInitializer;
 6 import io.netty.channel.EventLoopGroup;
 7 import io.netty.channel.nio.NioEventLoopGroup;
 8 import io.netty.channel.socket.SocketChannel;
 9 import io.netty.channel.socket.nio.NioSocketChannel;
10
11 import java.net.InetSocketAddress;
12
13 public class EchoClient {
14     private final String host;
15     private final int port;
16
17     public EchoClient() {
18         this(0);
19     }
20
21     public EchoClient(int port) {
22         this("localhost", port);
23     }
24
25     public EchoClient(String host, int port) {
26         this.host = host;
27         this.port = port;
28     }
29
30     public void start() throws Exception {
31         EventLoopGroup group = new NioEventLoopGroup();
32         try {
33             Bootstrap b = new Bootstrap();
34             b.group(group) // 注册线程池
35                     .channel(NioSocketChannel.class) // 使用NioSocketChannel来作为连接用的channel类
36                     .remoteAddress(new InetSocketAddress(this.host, this.port)) // 绑定连接端口和host信息
37                     .handler(new ChannelInitializer<SocketChannel>() { // 绑定连接初始化器
38                                 @Override
39                                 protected void initChannel(SocketChannel ch) throws Exception {
40                                     System.out.println("connected...");
41                                     ch.pipeline().addLast(new EchoClientHandler());
42                                 }
43                             });
44             System.out.println("created..");
45
46             ChannelFuture cf = b.connect().sync(); // 异步连接服务器
47             System.out.println("connected..."); // 连接完成
48
49             cf.channel().closeFuture().sync(); // 异步等待关闭连接channel
50             System.out.println("closed.."); // 关闭完成
51         } finally {
52             group.shutdownGracefully().sync(); // 释放线程池资源
53         }
54     }
55
56     public static void main(String[] args) throws Exception {
57         new EchoClient("127.0.0.1", 65535).start(); // 连接127.0.0.1/65535，并启动
58     }
59 }

　　连接成功后，具体的通信代码

 1 package com.gerry.netty.client;
 2
 3 import java.nio.charset.Charset;
 4
 5 import io.netty.buffer.ByteBuf;
 6 import io.netty.buffer.ByteBufUtil;
 7 import io.netty.buffer.Unpooled;
 8 import io.netty.channel.ChannelHandlerContext;
 9 import io.netty.channel.SimpleChannelInboundHandler;
10 import io.netty.util.CharsetUtil;
11
12 public class EchoClientHandler extends SimpleChannelInboundHandler<ByteBuf> {
13
14     @Override
15     public void channelActive(ChannelHandlerContext ctx) throws Exception {
16         System.out.println("client channelActive..");
17         ctx.writeAndFlush(Unpooled.copiedBuffer("Netty rocks!", CharsetUtil.UTF_8)); // 必须有flush
18
19         // 必须存在flush
20         // ctx.write(Unpooled.copiedBuffer("Netty rocks!", CharsetUtil.UTF_8));
21         // ctx.flush();
22     }
23
24     @Override
25     protected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {
26         System.out.println("client channelRead..");
27         ByteBuf buf = msg.readBytes(msg.readableBytes());
28         System.out.println("Client received:" + ByteBufUtil.hexDump(buf) + "; The value is:" + buf.toString(Charset.forName("utf-8")));
29         //ctx.channel().close().sync();// client关闭channel连接
30     }
31
32     @Override
33     public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
34         cause.printStackTrace();
35         ctx.close();
36     }
37
38 }

三、结果

　　先运行server，在运行client即可。

转载链接：http://www.cnblogs.com/liuming1992/p/4758532.html

以上netty使用的版本

<!-- https://mvnrepository.com/artifact/io.netty/netty-all -->
<dependency>
<groupId>io.netty</groupId>
<artifactId>netty-all</artifactId>
<version>4.1.6.Final</version>
</dependency>