惠州什么是Java异步套接字通道？_北大青鸟IT学校

什么是Java异步套接字通道？这是每个学习Java的同学都会遇到的问题，下面我们一起来看看惠州北大青鸟老师是怎么回答的。

使用以下两个套接字通道类来执行异步套接字操作：

java.nio.channels.AsynchronousServerSocketChannel
java.nio.channels.AsynchronousSocketChannel

以下代码显示如何创建使用异步服务器套接字通道的服务器应用程序。

实例

import java.io.IOException;import java.net.InetSocketAddress;import java.net.SocketAddress;import java.nio.ByteBuffer;import java.nio.channels.AsynchronousServerSocketChannel;import java.nio.channels.AsynchronousSocketChannel;import java.nio.channels.CompletionHandler;import java.nio.charset.Charset;public class Main {  public static void main(String[] args) throws Exception {
   AsynchronousServerSocketChannel server = AsynchronousServerSocketChannel
       .open();
   String host = "localhost";    int port = 8989;
   InetSocketAddress sAddr = new InetSocketAddress(host, port);
   server.bind(sAddr);
   System.out.format("Server is listening at %s%n", sAddr);
   Attachment attach = new Attachment();
   attach.server = server;
   server.accept(attach, new ConnectionHandler());
   Thread.currentThread().join();
 }
}class Attachment {
 AsynchronousServerSocketChannel server;
 AsynchronousSocketChannel client;
 ByteBuffer buffer;
 SocketAddress clientAddr;  boolean isRead;
}class ConnectionHandler implements
   CompletionHandler<AsynchronousSocketChannel, Attachment> {
 @Override  public void completed(AsynchronousSocketChannel client, Attachment attach) {    try {
     SocketAddress clientAddr = client.getRemoteAddress();
     System.out.format("Accepted a  connection from  %s%n", clientAddr);
     attach.server.accept(attach, this);
     ReadWriteHandler rwHandler = new ReadWriteHandler();
     Attachment newAttach = new Attachment();
     newAttach.server = attach.server;
     newAttach.client = client;
     newAttach.buffer = ByteBuffer.allocate(2048);
     newAttach.isRead = true;
     newAttach.clientAddr = clientAddr;
     client.read(newAttach.buffer, newAttach, rwHandler);
   } catch (IOException e) {
     e.printStackTrace();
   }
 }

 @Override  public void failed(Throwable e, Attachment attach) {
   System.out.println("Failed to accept a  connection.");
   e.printStackTrace();
 }
}class ReadWriteHandler implements CompletionHandler<Integer, Attachment> {
 @Override  public void completed(Integer result, Attachment attach) {    if (result == -1) {      try {
       attach.client.close();
       System.out.format("Stopped   listening to the   client %s%n",
           attach.clientAddr);
     } catch (IOException ex) {
       ex.printStackTrace();
     }      return;
   }    if (attach.isRead) {
     attach.buffer.flip();      int limits = attach.buffer.limit();      byte bytes[] = new byte[limits];
     attach.buffer.get(bytes, 0, limits);
     Charset cs = Charset.forName("UTF-8");
     String msg = new String(bytes, cs);
     System.out.format("Client at  %s  says: %s%n", attach.clientAddr,
         msg);
     attach.isRead = false; // It is a write      attach.buffer.rewind();

   } else {      // Write to the client      attach.client.write(attach.buffer, attach, this);
     attach.isRead = true;
     attach.buffer.clear();
     attach.client.read(attach.buffer, attach, this);
   }
 }

 @Override  public void failed(Throwable e, Attachment attach) {
   e.printStackTrace();
 }
}

上面的代码生成以下结果。

Server is listening at localhost/127.0.0.1:8989

...

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