Java NIO非堵塞应用通常适用用在I/O读写等方面，我们知道，系统运行的性能瓶颈通常在I/O读写，包括对端口和文件的操作上，过去，在打开一个I/O通道后，read()将一直等待在端口一边读取字节内容，如果没有内容进来，read()也是傻傻的等，这会影响我们程序继续做其他事情，那么改进做法就是开设线程，让线程去等待，但是这样做也是相当耗费资源的。
Java NIO非堵塞技术实际是采取Reactor模式，或者说是Observer模式为我们监察I/O端口，如果有内容进来，会自动通知我们，这样，我们就不必开启多个线程死等，从外界看，实现了流畅的I/O读写，不堵塞了。
Java NIO出现不只是一个技术性能的提高，你会发现网络上到处在介绍它，因为它具有里程碑意义，从JDK1.4开始，Java开始提高性能相关的功能，从而使得Java在底层或者并行分布式计算等操作上已经可以和C或Perl等语言并驾齐驱。
图 1 类结构图
package cn.chenkangxian.nioconcurrent;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.SocketChannel;
import java.util.LinkedList;
import java.util.List;
/**
* @Project: testNio
*
* @Author: chenkangxian
*
* @Annotation: 使用线程池来处理大量channel并发
*
* @Date:2011-7-5
*
* @Copyright: 2011 chenkangxian, All rights reserved.
*
*/
public class SelectSocketsThreadPool extends SelectSockets {
private static final int MAX_THREADS = 5;
private ThreadPool pool = new ThreadPool(MAX_THREADS);
/**
* 从socket中读数据
*/
protected void readDataFromSocket(SelectionKey key) throws Exception {
WorkerThread worker = pool.getWorker();
if (worker == null) {
return;
worker.serviceChannel(key);
}
/**
*
* @Project: concurrentnio
*
* @Author: chenkangxian
*
* @Annotation:线程池
*
* @Date:2011-7-20
*
* @Copyright: 2011 chenkangxian, All rights reserved.
*
*/
private class ThreadPool {
List idle = new LinkedList();
/**
* 线程池初始化
*
* @param poolSize 线程池大小
*/
ThreadPool(int poolSize) {
for (int i = 0; i < poolSize; i++) {
WorkerThread thread = new WorkerThread(this);
thread.setName("Worker" + (i + 1));
thread.start();
idle.add(thread);
}
}
/**
* 获得工作线程
*
* Author: chenkangxian
*
* Last Modification Time: 2011-7-20
*
* @return
*/
WorkerThread getWorker() {
WorkerThread worker = null;
synchronized (idle) {
if (idle.size() > 0) {
worker = (WorkerThread) idle.remove(0);
}
}
return (worker);
}
/**
* 送回工作线程
*
* Author: chenkangxian
*
* Last Modification Time: 2011-7-20
*
* @param worker
*/
void returnWorker(WorkerThread worker) {
synchronized (idle) {
idle.add(worker);
}
}
}
private class WorkerThread extends Thread {
private ByteBuffer buffer = ByteBuffer.allocate(1024);
private ThreadPool pool;
private SelectionKey key;
WorkerThread(ThreadPool pool) {
this.pool = pool;
}
public synchronized void run() {
System.out.println(this.getName() + " is ready");
while (true) {
try {
this.wait();//等待被notify
} catch (InterruptedException e) {
e.printStackTrace();
this.interrupt();
}
if (key == null) {//直到有key
continue;
}
System.out.println(this.getName() + " has been awakened");
try {
drainChannel(key);
} catch (Exception e) {
System.out.println("Caught '" + e + "' closing channel");
try {
key.channel().close();
} catch (IOException ex) {
ex.printStackTrace();
}
key.selector().wakeup();
}
key = null;
this.pool.returnWorker(this);
}
}
synchronized void serviceChannel(SelectionKey key) {
this.key = key;
//消除读的关注
key.interestOps(key.interestOps() & (~SelectionKey.OP_READ));
this.notify();
}
void drainChannel(SelectionKey key) throws Exception {
SocketChannel channel = (SocketChannel) key.channel();
int count;
buffer.clear();
while ((count = channel.read(buffer)) > 0) {
buffer.flip();
while (buffer.hasRemaining()) {
channel.write(buffer);
}
buffer.clear();
}
if (count < 0) {
channel.close();
return;
}
//重新开始关注读事件
key.interestOps(key.interestOps() | SelectionKey.OP_READ);
key.selector().wakeup();
}
}
public static void main(String[] args) throws Exception {
new SelectSocketsThreadPool().go(args);
}
}
- 1.
- 2.
- 3.
- 4.
- 5.
- 6.
- 7.
- 8.
- 9.
- 10.
- 11.
- 12.
- 13.
- 14.
- 15.
- 16.
- 17.
- 18.
- 19.
- 20.
- 21.
- 22.
- 23.
- 24.
- 25.
- 26.
- 27.
- 28.
- 29.
- 30.
- 31.
- 32.
- 33.
- 34.
- 35.
- 36.
- 37.
- 38.
- 39.
- 40.
- 41.
- 42.
- 43.
- 44.
- 45.
- 46.
- 47.
- 48.
- 49.
- 50.
- 51.
- 52.
- 53.
- 54.
- 55.
- 56.
- 57.
- 58.
- 59.
- 60.
- 61.
- 62.
- 63.
- 64.
- 65.
- 66.
- 67.
- 68.
- 69.
- 70.
- 71.
- 72.
- 73.
- 74.
- 75.
- 76.
- 77.
- 78.
- 79.
- 80.
- 81.
- 82.
- 83.
- 84.
- 85.
- 86.
- 87.
- 88.
- 89.
- 90.
- 91.
- 92.
- 93.
- 94.
- 95.
- 96.
- 97.
- 98.
- 99.
- 100.
- 101.
- 102.
- 103.
- 104.
- 105.
- 106.
- 107.
- 108.
- 109.
- 110.
- 111.
- 112.
- 113.
- 114.
- 115.
- 116.
- 117.
- 118.
- 119.
- 120.
- 121.
- 122.
- 123.
- 124.
- 125.
- 126.
- 127.
- 128.
- 129.
- 130.
- 131.
- 132.
- 133.
- 134.
- 135.
- 136.
- 137.
- 138.
- 139.
- 140.
- 141.
- 142.
- 143.
- 144.
- 145.
- 146.
- 147.
- 148.
- 149.
- 150.
- 151.
- 152.
- 153.
- 154.
- 155.
- 156.
- 157.
- 158.
- 159.
- 160.
- 161.
- 162.
package cn.chenkangxian.nioconcurrent;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.nio.ByteBuffer;
import java.nio.channels.SelectableChannel;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
/**
*
* @Project: concurrentnio
*
* @Author: chenkangxian
*
* @Annotation:
*
* @Date:2011-7-11
*
* @Copyright: 2011 chenkangxian, All rights reserved.
*
*/
public class SelectSockets {
public static int PORT_NUMBER = 1234;
private ByteBuffer buffer = ByteBuffer.allocate(1024);
public static void main(String[] args) throws Exception {
new SelectSockets().go(args);
}
public void go(String[] args) throws Exception{
int port = PORT_NUMBER;
// if(args.length > 0){
// port = Integer.parseInt(args[0]);
// }
// System.out.println("Listening on port " + port);
ServerSocketChannel serverChannel = ServerSocketChannel.open();
ServerSocket serverSocket = serverChannel.socket();
Selector selector = Selector.open();
serverSocket.bind(new InetSocketAddress(port));
serverChannel.configureBlocking(false);
serverChannel.register(selector, SelectionKey.OP_ACCEPT);
while(true){
int n = selector.select(); //没有轮询，单个selector
if(n == 0){
continue;
}
Iterator it = selector.selectedKeys().iterator();
while(it.hasNext()){
SelectionKey key = (SelectionKey)it.next();
if(key.isAcceptable()){
ServerSocketChannel server = (ServerSocketChannel)key.channel();
SocketChannel channel = server.accept(); registerChannel(selector,channel,SelectionKey.OP_READ);
sayHello(channel);
}
if(key.isReadable()){
readDataFromSocket(key);
}
it.remove();
}
}
}
/**
* 在selector上注册channel，并设置interest
*
* Author: chenkangxian
*
* Last Modification Time: 2011-7-11
*
* @param selector 选择器
*
* @param channel 通道
*
* @param ops interest
*
* @throws Exception
*/
protected void registerChannel(Selector selector,
SelectableChannel channel, int ops) throws Exception{
if(channel == null){
return ;
}
channel.configureBlocking(false);
channel.register(selector, ops);
}
/**
* 处理有可用数据的通道
*
* Author: chenkangxian
*
* Last Modification Time: 2011-7-11
*
* @param key 可用通道对应的key
*
* @throws Exception
*/
protected void readDataFromSocket(SelectionKey key) throws Exception{
SocketChannel socketChannel = (SocketChannel)key.channel();
int count;
buffer.clear(); //Empty buffer
while((count = socketChannel.read(buffer)) > 0){
buffer.flip();
while(buffer.hasRemaining()){
socketChannel.write(buffer);
}
buffer.clear();
}
if(count < 0){
socketChannel.close();
}
}
/**
* 打招呼
*
* Author: chenkangxian
*
* Last Modification Time: 2011-7-11
*
* @param channel 客户端channel
*
* @throws Exception
*/
private void sayHello(SocketChannel channel) throws Exception{
buffer.clear();
buffer.put("Hello 哈罗! \r\n".getBytes());
buffer.flip();
channel.write(buffer);
}
}
- 1.
- 2.
- 3.
- 4.
- 5.
- 6.
- 7.
- 8.
- 9.
- 10.
- 11.
- 12.
- 13.
- 14.
- 15.
- 16.
- 17.
- 18.
- 19.
- 20.
- 21.
- 22.
- 23.
- 24.
- 25.
- 26.
- 27.
- 28.
- 29.
- 30.
- 31.
- 32.
- 33.
- 34.
- 35.
- 36.
- 37.
- 38.
- 39.
- 40.
- 41.
- 42.
- 43.
- 44.
- 45.
- 46.
- 47.
- 48.
- 49.
- 50.
- 51.
- 52.
- 53.
- 54.
- 55.
- 56.
- 57.
- 58.
- 59.
- 60.
- 61.
- 62.
- 63.
- 64.
- 65.
- 66.
- 67.
- 68.
- 69.
- 70.
- 71.
- 72.
- 73.
- 74.
- 75.
- 76.
- 77.
- 78.
- 79.
- 80.
- 81.
- 82.
- 83.
- 84.
- 85.
- 86.
- 87.
- 88.
- 89.
- 90.
- 91.
- 92.
- 93.
- 94.
- 95.
- 96.
- 97.
- 98.
- 99.
- 100.
- 101.
- 102.
- 103.
- 104.
- 105.
- 106.
- 107.
- 108.
- 109.
- 110.
- 111.
- 112.
- 113.
- 114.
- 115.
- 116.
- 117.
- 118.
- 119.
- 120.
- 121.
- 122.
- 123.
- 124.
- 125.
- 126.
- 127.
- 128.
- 129.
- 130.
- 131.
原文链接：http://chenkangxian.iteye.com/blog/1288246
【编辑推荐】
