AIO編程
NIO 2.0引入了新的異步通道的概念,並提供了異步文件通道和異步套接字通道的實現。
異步的套接字通道時真正的異步非阻塞I/O,對應於UNIX網絡編程中的事件驅動I/O(AIO)。他不需要過多的Selector對註冊的通道進行輪詢即可實現異步讀寫,從而簡化了NIO的編程模型。
直接上代碼吧。
3.1、Server端代碼
Server:
package com.anxpp.io.calculator.aio.server;
/**
* AIO服務端
* @author yangtao__anxpp.com
* @version 1.0
*/
public class Server {
private static int DEFAULT_PORT = 12345;
private static AsyncServerHandler serverHandle;
public volatile static long clientCount = 0;
public static void start(){
start(DEFAULT_PORT);
}
public static synchronized void start(int port){
if(serverHandle!=null)
return;
serverHandle = new AsyncServerHandler(port);
new Thread(serverHandle,"Server").start();
}
public static void main(String[] args){
Server.start();
}
}
AsyncServerHandler:
package com.anxpp.io.calculator.aio.server;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.channels.AsynchronousServerSocketChannel;
import java.util.concurrent.CountDownLatch;
public class AsyncServerHandler implements Runnable {
public CountDownLatch latch;
public AsynchronousServerSocketChannel channel;
public AsyncServerHandler(int port) {
try {
//創建服務端通道
channel = AsynchronousServerSocketChannel.open();
//綁定端口
channel.bind(new InetSocketAddress(port));
System.out.println("服務器已啓動,端口號:" + port);
} catch (IOException e) {
e.printStackTrace();
}
}
@Override
public void run() {
//CountDownLatch初始化
//它的作用:在完成一組正在執行的操作之前,允許當前的現場一直阻塞
//此處,讓現場在此阻塞,防止服務端執行完成後退出
//也可以使用while(true)+sleep
//生成環境就不需要擔心這個問題,以爲服務端是不會退出的
latch = new CountDownLatch(1);
//用於接收客戶端的連接
channel.accept(this,new AcceptHandler());
try {
latch.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
AcceptHandler:
package com.anxpp.io.calculator.aio.server;
import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousSocketChannel;
import java.nio.channels.CompletionHandler;
//作爲handler接收客戶端連接
public class AcceptHandler implements CompletionHandler<AsynchronousSocketChannel, AsyncServerHandler> {
@Override
public void completed(AsynchronousSocketChannel channel,AsyncServerHandler serverHandler) {
//繼續接受其他客戶端的請求
Server.clientCount++;
System.out.println("連接的客戶端數:" + Server.clientCount);
serverHandler.channel.accept(serverHandler, this);
//創建新的Buffer
ByteBuffer buffer = ByteBuffer.allocate(1024);
//異步讀 第三個參數爲接收消息回調的業務Handler
channel.read(buffer, buffer, new ReadHandler(channel));
}
@Override
public void failed(Throwable exc, AsyncServerHandler serverHandler) {
exc.printStackTrace();
serverHandler.latch.countDown();
}
}
ReadHandler:
package com.anxpp.io.calculator.aio.server;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousSocketChannel;
import java.nio.channels.CompletionHandler;
import com.anxpp.io.utils.Calculator;
public class ReadHandler implements CompletionHandler<Integer, ByteBuffer> {
//用於讀取半包消息和發送應答
private AsynchronousSocketChannel channel;
public ReadHandler(AsynchronousSocketChannel channel) {
this.channel = channel;
}
//讀取到消息後的處理
@Override
public void completed(Integer result, ByteBuffer attachment) {
//flip操作
attachment.flip();
//根據
byte[] message = new byte[attachment.remaining()];
attachment.get(message);
try {
String expression = new String(message, "UTF-8");
System.out.println("服務器收到消息: " + expression);
String calrResult = null;
try{
calrResult = Calculator.cal(expression).toString();
}catch(Exception e){
calrResult = "計算錯誤:" + e.getMessage();
}
//向客戶端發送消息
doWrite(calrResult);
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
//發送消息
private void doWrite(String result) {
byte[] bytes = result.getBytes();
ByteBuffer writeBuffer = ByteBuffer.allocate(bytes.length);
writeBuffer.put(bytes);
writeBuffer.flip();
//異步寫數據 參數與前面的read一樣
channel.write(writeBuffer, writeBuffer,new CompletionHandler<Integer, ByteBuffer>() {
@Override
public void completed(Integer result, ByteBuffer buffer) {
//如果沒有發送完,就繼續發送直到完成
if (buffer.hasRemaining())
channel.write(buffer, buffer, this);
else{
//創建新的Buffer
ByteBuffer readBuffer = ByteBuffer.allocate(1024);
//異步讀 第三個參數爲接收消息回調的業務Handler
channel.read(readBuffer, readBuffer, new ReadHandler(channel));
}
}
@Override
public void failed(Throwable exc, ByteBuffer attachment) {
try {
channel.close();
} catch (IOException e) {
}
}
});
}
@Override
public void failed(Throwable exc, ByteBuffer attachment) {
try {
this.channel.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
OK,這樣就已經完成了,其實說起來也簡單,雖然代碼感覺很多,但是API比NIO的使用起來真的簡單多了,主要就是監聽、讀、寫等各種CompletionHandler。此處本應有一個WriteHandler的,確實,我們在ReadHandler中,以一個匿名內部類實現了它。
下面看客戶端代碼。
3.2、Client端代碼
Client:
package com.anxpp.io.calculator.aio.client;import java.util.Scanner;
public class Client {
private static String DEFAULT_HOST = "127.0.0.1";
private static int DEFAULT_PORT = 12345;
private static AsyncClientHandler clientHandle;
public static void start(){
start(DEFAULT_HOST,DEFAULT_PORT);
}
public static synchronized void start(String ip,int port){
if(clientHandle!=null)
return;
clientHandle = new AsyncClientHandler(ip,port);
new Thread(clientHandle,"Client").start();
}
//向服務器發送消息
public static boolean sendMsg(String msg) throws Exception{
if(msg.equals("q")) return false;
clientHandle.sendMsg(msg);
return true;
}
@SuppressWarnings("resource")
public static void main(String[] args) throws Exception{
Client.start();
System.out.println("請輸入請求消息:");
Scanner scanner = new Scanner(System.in);
while(Client.sendMsg(scanner.nextLine()));
}
}
AsyncClientHandler:
package com.anxpp.io.calculator.aio.client;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousSocketChannel;
import java.nio.channels.CompletionHandler;
import java.util.concurrent.CountDownLatch;
public class AsyncClientHandler implements CompletionHandler<Void, AsyncClientHandler>, Runnable {
private AsynchronousSocketChannel clientChannel;
private String host;
private int port;
private CountDownLatch latch;
public AsyncClientHandler(String host, int port) {
this.host = host;
this.port = port;
try {
//創建異步的客戶端通道
clientChannel = AsynchronousSocketChannel.open();
} catch (IOException e) {
e.printStackTrace();
}
}
@Override
public void run() {
//創建CountDownLatch等待
latch = new CountDownLatch(1);
//發起異步連接操作,回調參數就是這個類本身,如果連接成功會回調completed方法
clientChannel.connect(new InetSocketAddress(host, port), this, this);
try {
latch.await();
} catch (InterruptedException e1) {
e1.printStackTrace();
}
try {
clientChannel.close();
} catch (IOException e) {
e.printStackTrace();
}
}
//連接服務器成功
//意味着TCP三次握手完成
@Override
public void completed(Void result, AsyncClientHandler attachment) {
System.out.println("客戶端成功連接到服務器...");
}
//連接服務器失敗
@Override
public void failed(Throwable exc, AsyncClientHandler attachment) {
System.err.println("連接服務器失敗...");
exc.printStackTrace();
try {
clientChannel.close();
latch.countDown();
} catch (IOException e) {
e.printStackTrace();
}
}
//向服務器發送消息
public void sendMsg(String msg){
byte[] req = msg.getBytes();
ByteBuffer writeBuffer = ByteBuffer.allocate(req.length);
writeBuffer.put(req);
writeBuffer.flip();
//異步寫
clientChannel.write(writeBuffer, writeBuffer,new WriteHandler(clientChannel, latch));
}
}
WriteHandler:
package com.anxpp.io.calculator.aio.client;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousSocketChannel;
import java.nio.channels.CompletionHandler;
import java.util.concurrent.CountDownLatch;
public class WriteHandler implements CompletionHandler<Integer, ByteBuffer> {
private AsynchronousSocketChannel clientChannel;
private CountDownLatch latch;
public WriteHandler(AsynchronousSocketChannel clientChannel,CountDownLatch latch) {
this.clientChannel = clientChannel;
this.latch = latch;
}
@Override
public void completed(Integer result, ByteBuffer buffer) {
//完成全部數據的寫入
if (buffer.hasRemaining()) {
clientChannel.write(buffer, buffer, this);
}
else {
//讀取數據
ByteBuffer readBuffer = ByteBuffer.allocate(1024);
clientChannel.read(readBuffer,readBuffer,new ReadHandler(clientChannel, latch));
}
}
@Override
public void failed(Throwable exc, ByteBuffer attachment) {
System.err.println("數據發送失敗...");
try {
clientChannel.close();
latch.countDown();
} catch (IOException e) {
}
}
}
這個API使用起來真的是很順手。
3.3、測試
Test:
package com.anxpp.io.calculator.aio;import java.util.Scanner;
import com.anxpp.io.calculator.aio.client.Client;
import com.anxpp.io.calculator.aio.server.Server;
/**
* 測試方法
* @author yangtao__anxpp.com
* @version 1.0
*/
public class Test {
//測試主方法
@SuppressWarnings("resource")
public static void main(String[] args) throws Exception{
//運行服務器
Server.start();
//避免客戶端先於服務器啓動前執行代碼
Thread.sleep(100);
//運行客戶端
Client.start();
System.out.println("請輸入請求消息:");
Scanner scanner = new Scanner(System.in);
while(Client.sendMsg(scanner.nextLine()));
}
}
我們可以在控制檯輸入我們需要計算的算數字符串,服務器就會返回結果,當然,我們也可以運行大量的客戶端,都是沒有問題的,以爲此處設計爲單例客戶端,所以也就沒有演示大量客戶端併發。
讀者可以自己修改Client類,然後開闢大量線程,並使用構造方法創建很多的客戶端測試。
下面是其中一次參數的輸出:
下面是其中一次參數的輸出:- 服務器已啓動,端口號:12345
- 請輸入請求消息:
- 客戶端成功連接到服務器...
- 連接的客戶端數:1
- 123456+789+456
- 服務器收到消息: 123456+789+456
- 客戶端收到結果:124701
- 9526*56
- 服務器收到消息: 9526*56
- 客戶端收到結果:533456
- ...
AIO是真正的異步非阻塞的,所以,在面對超級大量的客戶端,更能得心應手。
下面就比較一下,幾種I/O編程的優缺點。