JDK7 AIO 入门（二）------AsynchronousServerSocketChannel

接上篇，接下来练习通过AIO实现一个简单的TCP server。熟悉NIO的朋友应该都了解ServerSocket，在AIO中与之对应的就是AsynchronousServerSocketChannel，查看其API文档，介绍如下”An asynchronous channel for stream-oriented listening sockets. “，就是一个异步的数据流监听Socket。其主要函数有如下几个： 

accept()： 接受一个连接，返回一个Future，可通过Future获取到Socket的状态，和数据。 
accept(A attachment, CompletionHandler<AsynchronousSocketChannel,? super A> handler)：接受连接，并为连接绑定一个CompletionHandler处理Socket连接 

bind(SocketAddress local)：把ServerSocket绑定到本地端口上，等待连接。 
bind(SocketAddress local, int backlog)：功能和上面一个方法一样，添加了backlog参数指定队列中挂起的连接的最大个数 

open()：开启一个异步Socket通道， 
open(AsynchronousChannelGroup group)：开启一个异步Socket通道，并把通道加入指定的组做资源管理 

provider()：返回这个Channel的创建者 

setOption(SocketOption<T> name, T value)：配置Socket参数的方法。 

下面就是通过AsynchronousServerSocketChannel实现的一个简单的EchoServer，服务器会打印出收到的客户端输入，并把输入写回客户端。（注：代码只有在JDK1.7下才能编译通过）

public class AIOEchoServer {    private AsynchronousServerSocketChannel server;    public static void main(String[] args) throws IOException {        AIOEchoServer aioServer = new AIOEchoServer();        aioServer.init("localhost", 6025);    }    private void init(String host, int port) throws IOException {        //ChannelGroup用来管理共享资源        AsynchronousChannelGroup group = AsynchronousChannelGroup.withCachedThreadPool(Executors.newCachedThreadPool(), 10);        server = AsynchronousServerSocketChannel.open(group);        //通过setOption配置Socket        server.setOption(StandardSocketOptions.SO_REUSEADDR, true);        server.setOption(StandardSocketOptions.SO_RCVBUF, 16 * 1024);        //绑定到指定的主机，端口        server.bind(new InetSocketAddress(host, port));        System.out.println("Listening on " + host + ":" + port);        //输出provider        System.out.println("Channel Provider : " + server.provider());        //等待连接，并注册CompletionHandler处理内核完成后的操作。        server.accept(null, new CompletionHandler<AsynchronousSocketChannel, Object>() {            final ByteBuffer buffer = ByteBuffer.allocate(1024);            @Override            public void completed(AsynchronousSocketChannel result, Object attachment) {                System.out.println("waiting....");                buffer.clear();                try {                    //把socket中的数据读取到buffer中                    result.read(buffer).get();                    buffer.flip();                    System.out.println("Echo " + new String(buffer.array()).trim() + " to " + result);                                       //把收到的直接返回给客户端                    result.write(buffer);                    buffer.flip();                } catch (InterruptedException e) {                    e.printStackTrace();                } catch (ExecutionException e) {                    e.printStackTrace();                } finally {                    try {                        //关闭处理完的socket，并重新调用accept等待新的连接                        result.close();                        server.accept(null, this);                    } catch (IOException e) {                        e.printStackTrace();                    }                }            }            @Override            public void failed(Throwable exc, Object attachment) {                System.out.print("Server failed...." + exc.getCause());            }        });        //因为AIO不会阻塞调用进程，因此必须在主进程阻塞，才能保持进程存活。        try {            Thread.sleep(Integer.MAX_VALUE);        } catch (InterruptedException e) {            e.printStackTrace();        }    }}

运行时会打印出如下信息： 
Listening on localhost:6025 
Channel Provider : sun.nio.ch.BsdAsynchronousChannelProvider@625cb0bb 


在客户端，可以通过telnet localhost 6025验证服务 
Trying ::1... 
telnet: connect to address ::1: Connection refused 
Trying 127.0.0.1... 
Connected to localhost. 
Escape character is '^]'. 

输入 hello，回车，客户端会打印 
hello 
hello 
Connection closed by foreign host. 

服务器端会有打印 
waiting.... 
Echo hello to sun.nio.ch.UnixAsynchronousSocketChannelImpl[connected local=/127.0.0.1:6025 remote=/127.0.0.1:54611]