Java新AIO/NIO2：以CompletionHandler实现 AsynchronousServerSocketChannel服务器端

青旅半醒 2024-02-19 18:22 14阅读 0赞

## Java新AIO/NIO2：以CompletionHandler实现 AsynchronousServerSocketChannel服务器端程序代码 ##

import java.net.InetSocketAddress;
    import java.net.StandardSocketOptions;
    import java.nio.ByteBuffer;
    import java.nio.channels.AsynchronousChannelGroup;
    import java.nio.channels.AsynchronousServerSocketChannel;
    import java.nio.channels.AsynchronousSocketChannel;
    import java.nio.channels.CompletionHandler;
    import java.util.concurrent.Executors;
    import java.util.concurrent.Future;
    
    public class Server {
    	private AsynchronousServerSocketChannel serverSocketChannel;
    	
    	public static void main(String[] args) {
    		try {
    			Server server = new Server();
    		} catch (Exception e) {
    			e.printStackTrace();
    		}
    	}
    
    	public Server() throws Exception {
    		//AsynchronousChannelGroup group = AsynchronousChannelGroup.withCachedThreadPool(Executors.newCachedThreadPool(),10);
    		//serverSocketChannel = AsynchronousServerSocketChannel.open(group);
    		serverSocketChannel = AsynchronousServerSocketChannel.open();
    
    		InetSocketAddress inetSocketAddress = new InetSocketAddress("localhost", 80);
    
    		//serverSocketChannel.setOption(StandardSocketOptions.SO_REUSEADDR, true);
    		//serverSocketChannel.setOption(StandardSocketOptions.SO_RCVBUF, 16 * 1024);
    
    		serverSocketChannel.bind(inetSocketAddress);
    
    		MyCompletionHandler completionHandler = new MyCompletionHandler();
    		serverSocketChannel.accept(null, completionHandler);
    
    		// AIO非阻塞，需要在主进程阻塞，否则进程退出导致套接字关闭，服务器接受不到任何连接。
    		try {
    			Thread.sleep(Integer.MAX_VALUE);
    		} catch (InterruptedException e) {
    			e.printStackTrace();
    		}
    	}
    
    	private class MyCompletionHandler implements CompletionHandler<AsynchronousSocketChannel, Object> {
    		@Override
    		public void completed(AsynchronousSocketChannel socketChannel, Object attachment) {
    			System.out.println("服务器接受连接");
    			try {
    				sendDataToClient(socketChannel);
    				
    				serverSocketChannel.accept(null, this);
    			} catch (Exception e) {
    				e.printStackTrace();
    			}
    		}
    
    		@Override
    		public void failed(Throwable t, Object attachment) {
    			t.printStackTrace();
    		};
    	}
    
    	private void sendDataToClient(AsynchronousSocketChannel socketChannel) throws Exception {
    		System.out.println("服务器与" + socketChannel.getRemoteAddress() + "建立连接");
    
    		ByteBuffer buffer = ByteBuffer.wrap("zhangphil".getBytes());
    		Future<Integer> write = socketChannel.write(buffer);
    
    		while (!write.isDone()) {
    			Thread.sleep(10);
    		}
    
    		System.out.println("服务器发送数据完毕.");
    		socketChannel.close();
    	}
    }

用CompletionHandler实现 的AsynchronousServerSocketChannel服务器端程序代码，有一个问题在于需要额外的通过Thread.sleep(Integer.MAX\_VALUE)让当前进程无限休眠，因为担心程序退出，程序不退出的前提下，才能够让  
serverSocketChannel.accept(null, completionHandler);  
继续可以回调接受来自客户端的连接，当客户端的连接请求在CompletionHandler完成后，继续在CompletionHandler的completed()里面调用accept()函数等待客户端连接请求。

这种方案必须保证程序不能退出，一旦退出就会导致应用进程被杀掉，那么serverSocketChannel.accept(null, completionHandler) 就完全失效。或者换成我前一篇写的那种形式：

while (true){
        Future<AsynchronousSocketChannel> future = serverSocketChannel.accept();
        AsynchronousSocketChannel socketChannel = null;
        try {
            socketChannel = future.get();
            socketChannel.write(ByteBuffer.wrap("zhangphil".getBytes()));
         }catch (Exception e){
            e.printStackTrace();
         }
    }