我应该如何使用AsynchronousServerSocketChannel接受连接？

Question

我想用Java 7和NIO 2编写一个异步服务器.

但是我应该如何使用AsynchronousServerSocketChannel？

例如,如果我开始:

final AsynchronousServerSocketChannel server = 
    AsynchronousServerSocketChannel.open().bind(
        new InetSocketAddress(port));

然后,当我这样做时server.accept(),程序终止,因为该调用是异步的.如果我将该代码置于无限循环中,AcceptPendingException则抛出一个.

有关如何编写简单异步服务器的任何建议AsynchronousServerSocketChannel？

这是我的完整示例(类似于JavaDoc中的示例):

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.channels.AsynchronousServerSocketChannel;
import java.nio.channels.AsynchronousSocketChannel;
import java.nio.channels.CompletionHandler;

public class AsyncServer {

    public static void main(String[] args) {
        int port = 8060;
        try {
            final AsynchronousServerSocketChannel server = 
                    AsynchronousServerSocketChannel.open().bind(
                            new InetSocketAddress(port));

            System.out.println("Server listening on " + port);

            server.accept("Client connection", 
                    new CompletionHandler<AsynchronousSocketChannel, Object>() {
                public void completed(AsynchronousSocketChannel ch, Object att) {
                    System.out.println("Accepted a connection");

                    // accept the next connection
                    server.accept("Client connection", this);

                    // handle this connection
                    //TODO handle(ch);
                }

                public void failed(Throwable exc, Object att) {
                    System.out.println("Failed to accept connection");
                }
            });
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Answer 1

你在正确的轨道上,从完成的回调中调用accept()以接受更多连接应该工作.

一个简单(但丑陋)的方法来阻止线程终止只是循环直到线程被中断.

// yes, sleep() is evil, but sometimes I don't care
while (true) {
    Thread.sleep(1000);
}

更清洁的方法是使用AsynchronousChannelGroup.例如:

AsynchronousChannelGroup group = AsynchronousChannelGroup.withThreadPool(Executors
            .newSingleThreadExecutor());
AsynchronousServerSocketChannel server = AsynchronousServerSocketChannel.open(group).bind(
            new InetSocketAddress(port));

// (insert server.accept() logic here)

// wait until group.shutdown()/shutdownNow(), or the thread is interrupted:
group.awaitTermination(Long.MAX_VALUE, TimeUnit.SECONDS);

您可以调整线程的处理方式,有关详细信息,请参阅AsynchronousChannelGroup API文档.