Netty入门

小咪咪 2021-12-19 22:13 345阅读 0赞

## 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

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