Netty系列之一开始使用

Netty是用来做什么的呢，我的理解是它是一个网络开发框架，利用它能很快速方便的开发出高性能的服务端和客户端。刚开始学习java的时候你一定接触过怎么利用socket去实现服务端和客户端，后来java出了NIO这一大利器极大提供了网络程序的性能，但是NIO是基于事件驱动的模型，理解起来比常用的套接字编程要难一点，但是无论是利用NIO还是原始的socket编程从0开始编写一个服务端或是客户端实在是太困难了。Netty就是帮助你去解决这样的问题的，废话不多说先简单介绍一个例子，我们要写一个服务端绑定端口号后，等待客户端的连接，客户端连接后打印一句欢迎语句，然后客户端输入什么，服务端打印出来，并且返回给客户端输出，利用netty实现如下

 public class Server {

     private ServerBootstrap serverBootstrap;

     private int port;

     public Server(int port) {
         this.port = port;
         serverBootstrap = new ServerBootstrap(
                 new NioServerSocketChannelFactory(Executors.newCachedThreadPool(),
                         Executors.newCachedThreadPool()));
         serverBootstrap.setPipelineFactory(new ChannelPipelineFactory() {
             public ChannelPipeline getPipeline() throws Exception {
                 ChannelPipeline channelPipeline = Channels.pipeline();
                 channelPipeline.addLast("decoder", new StringDecoder());
                 channelPipeline.addLast("encoder", new StringEncoder());
                 channelPipeline.addLast("serverHandler", new ServerHandler());
                 return channelPipeline;
             }
         });
         serverBootstrap.bind(new InetSocketAddress(this.port));
     }

     private class ServerHandler extends SimpleChannelUpstreamHandler {
         @Override
         public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
             if(e.getMessage() instanceof String) {
                 String message = (String) e.getMessage();
                 System.out.println("Client Send:" + message);
                 e.getChannel().write("Server receive:" + message);
             }
         }

         @Override
         public void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
             System.out.println("A client connected to this server");
             System.out.println("Client:" + e.getChannel().getRemoteAddress());
             e.getChannel().write("******************************\r\n");
             e.getChannel().write("Welcome to connect this server\r\n");
             e.getChannel().write("******************************\r\n");
         }
     }

     public static void main(String args[]) {
         new Server(9999);
     }
 }