JDK1.7升級了NIO類庫，升級後的NIO類庫被稱爲NIO2.0。同時，Java正式提供了異步文件IO操作，同時提供給了與UNIX網絡編程事件驅動IO對應的AIO。
NIO2.0引入了新的異步通道的概念，提供了異步文件通道和異步套接字通道的實現。異步通道以兩種方式獲取操作結果。
通過java.util.concurrent.Future來來獲取異步操作的結果；
在執行異步操作的時候傳入一個java.nio.channels。
NIO2.0的異步套接字是真正的異步非阻塞IO，對應UNIX網絡編程中的事件驅動IO，即AIO。它不需要通過多路複用選擇器Selector對註冊的通道進行輪詢操作即可實現異步讀寫，簡化了NIO的編程模型。服務器代碼：
package com.test.aio;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
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.CountDownLatch;
/**
* AIO編程服務器端
* @author 程就人生
* @Date
*/
public class HelloServer {
public static void main( String[] args ){
int port = 8080;
AsyncHelloServerHandler helloServer = new AsyncHelloServerHandler(port);
new Thread(helloServer,"AIO").start();
}
}
/**
* AIO編程handler處理類
* @author 程就人生
* @Date
*/
class AsyncHelloServerHandler implements Runnable{
private int port;
CountDownLatch latch;
AsynchronousServerSocketChannel asynchronousServerSocketChannel;
public AsyncHelloServerHandler(int port) {
this.port = port;
try {
// 創建一個異步的服務端通道
asynchronousServerSocketChannel = AsynchronousServerSocketChannel.open();
// 綁定監聽端口
asynchronousServerSocketChannel.bind(new InetSocketAddress(port));
System.out.println("AIO編程，服務器端已啓動，啓動端口號爲：" + port);
} catch (IOException e) {
e.printStackTrace();
}
}
public void run() {
// 完成一組正在執行的操作之前，允許當前的線程一直阻塞
latch = new CountDownLatch(1);
// 接收客戶端的連接
doAccept();
try{
latch.await();
}catch(InterruptedException e){
e.printStackTrace();
}
}
private void doAccept() {
asynchronousServerSocketChannel.accept(this, new AcceptCompletionHandler());
}
}
/**
* 接收新的客戶端連接
* @author 程就人生
* @Date
*/
class AcceptCompletionHandler implements CompletionHandler<AsynchronousSocketChannel, AsyncHelloServerHandler>{
public void completed(AsynchronousSocketChannel result, AsyncHelloServerHandler attachment) {
attachment.asynchronousServerSocketChannel.accept(attachment, this);
ByteBuffer buffer = ByteBuffer.allocate(1024);
result.read(buffer, buffer, new ReadCompletionHandler(result));
}
public void failed(Throwable exc, AsyncHelloServerHandler attachment) {
attachment.latch.countDown();
}
}
/**
* 接收通知回調處理的handler
* @author 程就人生
* @Date
*/
class ReadCompletionHandler implements CompletionHandler<Integer, ByteBuffer>{
private AsynchronousSocketChannel channel;
public ReadCompletionHandler(AsynchronousSocketChannel channel) {
this.channel = channel;
}
public void completed(Integer result, ByteBuffer attachment) {
attachment.flip();
byte[] body = new byte[attachment.remaining()];
attachment.get(body);
try {
String req = new String(body, "utf-8");
System.out.println("服務器端收到的：" + req);
// 應答
doWrite();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
private void doWrite() {
byte[] bytes = "服務器端的反饋消息".getBytes();
// 發送緩衝區
ByteBuffer writeBuffer = ByteBuffer.allocate(bytes.length);
writeBuffer.put(bytes);
writeBuffer.flip();
channel.write(writeBuffer, writeBuffer, new CompletionHandler<Integer, ByteBuffer>(){
public void completed(Integer result, ByteBuffer buffer) {
// 如果沒有發送完，繼續發送
if(buffer.hasRemaining()){
channel.write(buffer, buffer, this);
}
}
public void failed(Throwable exc, ByteBuffer buffer) {
try {
channel.close();
} catch (IOException e) {
e.printStackTrace();
}
}
});
}
public void failed(Throwable exc, ByteBuffer attachment) {
try {
this.channel.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
在AsyncHelloServerHandler 的構造方法中，首先創建一個異步的服務器端通道AsynchronousServerSocketChannel，然後調用bind方法綁定監聽端口。
在線程run方法中，初始化CountDownLatch對象，完成一組正在執行的操作之前，允許當前的線程一直阻塞，防止服務器端執行完退出，實際項目中不需要。
使用doAccept方法接收客戶端的連接，因爲是異步操作，在這裏傳遞一個CompletionHandler類型的handler實例接收accept操作成功的通知消息。在AcceptCompletionHandler 類中可以接收新加入的客戶端連接。在77行預分配1KB的緩衝區。78行調用read進行異步讀操作。
在118行先進行flip操作，爲後續從緩衝區讀取數據做準備。根據緩衝區的可讀字節數創建byte數據組，通過new String對字節數組進行編碼，並打印出來。最後通過doWrite回寫客戶端。
客戶端代碼：
package com.test.aio;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousSocketChannel;
import java.nio.channels.CompletionHandler;
import java.util.concurrent.CountDownLatch;
/**
* AIO編程客戶端
* @author 程就人生
* @Date
*/
public class HelloClient {
public static void main( String[] args ){
int port = 8080;
new Thread(new AsyncHelloHandler("127.0.0.1",port)).start();
}
}
class AsyncHelloHandler implements CompletionHandler<Void, AsyncHelloHandler>, Runnable{
private String host;
private int port;
private AsynchronousSocketChannel client;
private CountDownLatch latch;
public AsyncHelloHandler(String host, int port) {
this.host = host;
this.port = port;
try {
client = AsynchronousSocketChannel.open();
} catch (IOException e) {
e.printStackTrace();
}
}
public void run() {
latch = new CountDownLatch(1);
client.connect(new InetSocketAddress(host, port), this, this);
try {
latch.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
try {
client.close();
} catch (IOException e) {
e.printStackTrace();
}
}
public void completed(Void result, AsyncHelloHandler attachment) {
byte[] req = "客戶端的消息".getBytes();
ByteBuffer writeBuffer = ByteBuffer.allocate(req.length);
writeBuffer.put(req);
writeBuffer.flip();
client.write(writeBuffer,writeBuffer, new CompletionHandler<Integer, ByteBuffer>(){
public void completed(Integer result, ByteBuffer buffer) {
if(buffer.hasRemaining()){
client.write(buffer, buffer, this);
}else{
ByteBuffer readBuffer = ByteBuffer.allocate(1024);
client.read(readBuffer, readBuffer, new CompletionHandler<Integer, ByteBuffer>(){
public void completed(Integer result, ByteBuffer buffer) {
buffer.flip();
byte[] bytes = new byte[buffer.remaining()];
buffer.get(bytes);
try {
String body = new String(bytes, "utf-8");
System.out.println("客戶端讀取到的：" + body);
latch.countDown();
System.out.println("客戶端操作完畢，關閉連接");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
public void failed(Throwable exc, ByteBuffer buffer) {
try {
client.close();
latch.countDown();
} catch (IOException e) {
e.printStackTrace();
}
}
});
}
}
public void failed(Throwable exc, ByteBuffer attachment) {
try {
client.close();
latch.countDown();
} catch (IOException e) {
e.printStackTrace();
}
}
});
}
public void failed(Throwable exc, AsyncHelloHandler attachment) {
try {
client.close();
latch.countDown();
} catch (IOException e) {
e.printStackTrace();
}
}
}
在20行，客戶端通過一個獨立的線程創建異步客戶端處理handler。在AsyncHelloHandler中，使用了大量匿名內部類。第38行，通過AsynchronousSocketChannel的open方法創建了一個新的AsynchronousSocketChannel對象。
在第45行，創建CountDownLatch進行等待，防止異步操咋沒有執行完線程就退出了。在第46行，通過connect方法發起異步操作。
在第73行，completed異步連接成功之後的方法回調，創建請求消息體，對bytebuffer進行flip，併發給服務器端。發送給服務器端後，接收服務器端的反饋，並進行打印，最後調用latch的countDown()方法，關閉客戶端連接。
服務器端執行結果：
客戶端執行結果：
以上便是來自java.nio包的非阻塞異步服務器端、客戶端編碼的簡單演示。