java中的AIO

AIO（异步非阻塞）AIO采用了Proactor模式，AIO与NIO的不同之处在于当AIO在进行读写操作时，不用先等通知，可直接调用相应的read/write方法，这两种方法均为异步的，对于读操作而言，当有流可读取时，操作系统会将可读的流传入read方法的缓冲区，并通知应用程序；对于写操作而言，当操作系统将write方法传递的流写入完毕时，操作系统主动通知应用程序,而NIO的通知是发生在动作之前的，是在可读、写的时候，Selector发现了这些事件后调用Handler处理.

在AIO socket编程中，服务端通道是AsynchronousServerSocketChannel，这个类提供了一个open()静态工厂，一个bind()方法用于绑定服务端IP地址（还有端口号），另外还提供了accept()用于接收用户连接请求。在客户端使用的通道是AsynchronousSocketChannel,这个通道处理提供open静态工厂方法外，还提供了read和write方法。

在AIO编程中，发出一个事件（accept read write等）之后要指定事件处理类（回调函数），AIO中的事件处理类是CompletionHandler<V,A>，这个接口定义了如下两个方法，分别在异步操作成功和失败时被回调。

void completed(V result, A attachment);

void failed(Throwable exc, A attachment);

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousServerSocketChannel;
import java.nio.channels.AsynchronousSocketChannel;
import java.nio.channels.CompletionHandler;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
public class AIOEchoServer {
public final static int PORT = 8001;
public final static String IP = "127.0.0.1";
private AsynchronousServerSocketChannel server = null;
public AIOEchoServer(){
try {
//同样是利用工厂方法产生一个通道，异步通道 AsynchronousServerSocketChannel
server = AsynchronousServerSocketChannel.open().bind(new InetSocketAddress(IP,PORT));
} catch (IOException e) {
e.printStackTrace();
}
}
//使用这个通道(server)来进行客户端的接收和处理
public void start(){
System.out.println("Server listen on "+PORT);
//注册事件和事件完成后的处理器，这个CompletionHandler就是事件完成后的处理器
server.accept(null,new CompletionHandler<AsynchronousSocketChannel,Object>(){
final ByteBuffer buffer = ByteBuffer.allocate(1024);
@Override
public void completed(AsynchronousSocketChannel result,Object attachment) {
System.out.println(Thread.currentThread().getName());
Future<Integer> writeResult = null;
try{
buffer.clear();
result.read(buffer).get(100,TimeUnit.SECONDS);
System.out.println("In server: "+ new String(buffer.array()));
//将数据写回客户端
buffer.flip();
writeResult = result.write(buffer);
}catch(InterruptedException | ExecutionException | TimeoutException e){
e.printStackTrace();
}finally{
server.accept(null,this);
try {
writeResult.get();
result.close();
} catch (InterruptedException | ExecutionException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
@Override
public void failed(Throwable exc, Object attachment) {
System.out.println("failed:"+exc);
}
});
}
public static void main(String[] args) {
new AIOEchoServer().start();
while(true){
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}

客户端：

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousSocketChannel;
import java.nio.channels.CompletionHandler;
public class AIOClient {
public static void main(String[] args) throws IOException {
final AsynchronousSocketChannel client = AsynchronousSocketChannel.open();
InetSocketAddress serverAddress = new InetSocketAddress("127.0.0.1",8001);
CompletionHandler<Void, ? super Object> handler = new CompletionHandler<Void,Object>(){
@Override
public void completed(Void result, Object attachment) {
client.write(ByteBuffer.wrap("Hello".getBytes()),null,
new CompletionHandler<Integer,Object>(){
@Override
public void completed(Integer result,
Object attachment) {
final ByteBuffer buffer = ByteBuffer.allocate(1024);
client.read(buffer,buffer,new CompletionHandler<Integer,ByteBuffer>(){
@Override
public void completed(Integer result,
ByteBuffer attachment) {
buffer.flip();
System.out.println(new String(buffer.array()));
try {
client.close();
} catch (IOException e) {
e.printStackTrace();
}
}
@Override
public void failed(Throwable exc,
ByteBuffer attachment) {
}
});
}
@Override
public void failed(Throwable exc, Object attachment) {
}
});
}
@Override
public void failed(Throwable exc, Object attachment) {
}
};
client.connect(serverAddress, null, handler);
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}

巴特西

java中的AIO

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