JDK7新特性<八>异步io/AIO

概述

JDK7引入了Asynchronous I/O。I/O编程中，常用到两种模式：Reactor 和 Proactor。Reactor就是Java的NIO。当有事件触发时，我们得到通知，进行相应的处理。Proactor就是我们今天要讲的 AIO了。AIO进行I/O操作，都是异步处理，当事件完成时，我们会得到通知。

JDK7的 AIO包括网络和文件操作。两者大同小异，本文通过一个完整的客户端/服务器Sample来详细说明aio的网络操作。

AIO提供了两种异步操作的监听机制。第一种通过返回一个Future对象来事件，调用其get（）会等到操作完成。第二种类似于回调函数。在进行异步操作时，传递一个CompletionHandler，当异步操作结束时，会调用CompletionHandler.complete 接口

范例

这个范例功能比较简单，就是客户端向服务端发送一个“test”命令，然后结束。

服务端程序 Sever.java

Java代码

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousServerSocketChannel;
import java.nio.channels.AsynchronousSocketChannel;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
public class Server {
private AsynchronousServerSocketChannel server;
public Server()throws IOException{
server = AsynchronousServerSocketChannel.open().bind(new InetSocketAddress(8888));
}
public void start() throws InterruptedException, ExecutionException, TimeoutException{
Future<AsynchronousSocketChannel> future = server.accept();
AsynchronousSocketChannel socket = future.get();
ByteBuffer readBuf = ByteBuffer.allocate(1024);
socket.read(readBuf).get(100, TimeUnit.SECONDS);
System.out.printf("Receiver:%s%n",new String(readBuf.array()));
}
public static void main(String args[]) throws Exception{
new Server().start();
}
}

客户端程序（Future版本）

Java代码

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousSocketChannel;
import java.util.concurrent.ExecutionException;
public class AIOClientWithFuture {
private final AsynchronousSocketChannel client;
public AIOClientWithFuture() throws IOException{
client = AsynchronousSocketChannel.open();
}
public void sendMsg() throws InterruptedException, ExecutionException{
client.connect(new InetSocketAddress("localhost",8888));
client.write(ByteBuffer.wrap("test".getBytes())).get();
}
public static void main(String...args) throws Exception{
AIOClientWithFuture client = new AIOClientWithFuture();
client.sendMsg();
}
}

客户端程序（CompleteHandler版本）

Java代码

import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousSocketChannel;
import java.nio.channels.CompletionHandler;
public class AIOClientWithHandler {
private final AsynchronousSocketChannel client ;
public AIOClientWithHandler() throws Exception{
client = AsynchronousSocketChannel.open();
}
public void start()throws Exception{
client.connect(new InetSocketAddress("127.0.0.1",8888),null,new CompletionHandler<Void,Void>() {
@Override
public void completed(Void result, Void attachment) {
try {
client.write(ByteBuffer.wrap("test".getBytes())).get();
} catch (Exception ex) {
ex.printStackTrace();
}
}
@Override
public void failed(Throwable exc, Void attachment) {
exc.printStackTrace();
}
});
}
public static void main(String args[])throws Exception{
new AIOClientWithHandler().start();
}
}