Netty入门

第二部分 Netty入门

netty可以运用在那些领域？
1分布式进程通信
例如: hadoop、dubbo、akka等具有分布式功能的框架，底层RPC通信都是基于netty实现的，这些框架使用的版本通常都还在用netty3.x

2、游戏服务器开发
最新的游戏服务器有部分公司可能已经开始采用netty4.x 或 netty5.x

服务器端

public class Server {

   public static void main(String[] args) {
  //服务类
  ServerBootstrap bootstrap = new ServerBootstrap();
  
  //boss线程监听端口，worker线程负责数据读写
  ExecutorService boss = Executors.newCachedThreadPool();
 ExecutorService worker = Executors.newCachedThreadPool();
  
  //设置niosocket工厂
  bootstrap.setFactory(new NioServerSocketChannelFactory(boss, worker));
  
  //设置管道的工厂
  bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
     
     @Override
     public ChannelPipeline getPipeline() throws Exception {

        ChannelPipeline pipeline = Channels.pipeline();
        pipeline.addLast("decoder", new StringDecoder());
        pipeline.addLast("encoder", new StringEncoder());
        pipeline.addLast("helloHandler", new HelloHandler());
        return pipeline;
     }
  });
  bootstrap.bind(new InetSocketAddress(10101));
  System.out.println("start!!!");
  
   }

}

客户端

public class Client {

   public static void main(String[] args) {
  
  //服务类
  ClientBootstrap bootstrap = new  ClientBootstrap();
  
  //线程池
  ExecutorService boss = Executors.newCachedThreadPool();
  ExecutorService worker = Executors.newCachedThreadPool();
  
  //socket工厂
  bootstrap.setFactory(new NioClientSocketChannelFactory(boss, worker));
  
  //管道工厂
  bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
     
     @Override
     public ChannelPipeline getPipeline() throws Exception {
        ChannelPipeline pipeline = Channels.pipeline();
        pipeline.addLast("decoder", new StringDecoder());
        pipeline.addLast("encoder", new StringEncoder());
        pipeline.addLast("hiHandler", new HiHandler());
        return pipeline;
     }
  });
  
  //连接服务端
  ChannelFuture connect = bootstrap.connect(new InetSocketAddress("127.0.0.1", 10101));
  Channel channel = connect.getChannel();
  
  System.out.println("client start");
  
  Scanner scanner = new Scanner(System.in);
  while(true){
     System.out.println("请输入");
     channel.write(scanner.next());
  }


  }

}

消息封装处理类

无论客户端或者服务器端都存在消息处理类，通过继承SimpleChannelHandler抽象类来实现，这里以服务器端封装类举例：

public class HelloHandler extends SimpleChannelHandler {

   /**
    * 接收消息
    */
   @Override
   public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
  
  String s = (String) e.getMessage();
  System.out.println(s);
  
  //回写数据
  ctx.getChannel().write("hi");
  super.messageReceived(ctx, e);
   }

   /**
    * 捕获异常
    */
   @Override
   public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) throws Exception {
      System.out.println("exceptionCaught");
      super.exceptionCaught(ctx, e);
   }

   /**
    * 新连接
    */
   @Override
   public void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
      System.out.println("channelConnected");
      super.channelConnected(ctx, e);
   }

   /**
    * 必须是链接已经建立，关闭通道的时候才会触发
    */
   @Override
   public void channelDisconnected(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
      System.out.println("channelDisconnected");
      super.channelDisconnected(ctx, e);
   }

   /**
    * channel关闭的时候触发
    */
   @Override
   public void channelClosed(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
      System.out.println("channelClosed");
      super.channelClosed(ctx, e);
   }
}

• messageReceived接收消息
• channelConnected新连接，通常用来检测IP是否是黑名单
• channelDisconnected已经建立好的连接关闭，可以再用户断线的时候清楚用户的缓存数据等
• channelClosed无论连接是否成功都会调用关闭资源