Java NIO就绪模式怎么实现

这篇文章主要介绍“Java NIO就绪模式怎么实现”，在日常操作中，相信很多人在Java NIO就绪模式怎么实现问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答”Java NIO就绪模式怎么实现”的疑惑有所帮助！接下来，请跟着小编一起来学习吧！

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;   public class SelectSocketsThreadPool extends SelectSockets {      private static final int MAX_THREADS = 5;     private ThreadPool pool = new ThreadPool(MAX_THREADS);           protected void readDataFromSocket(SelectionKey key) throws Exception {         WorkerThread worker = pool.getWorker();         if (worker == null) {             return;         worker.serviceChannel(key);     }          private class ThreadPool {         List idle = new LinkedList();                  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);             }         }                  WorkerThread getWorker() {             WorkerThread worker = null;              synchronized (idle) {                 if (idle.size() > 0) {                     worker = (WorkerThread) idle.remove(0);                 }             }             return (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);     } }

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;  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();             }         }     }          protected void registerChannel(Selector selector,             SelectableChannel channel, int ops) throws Exception{         if(channel == null){             return ;          }         channel.configureBlocking(false);         channel.register(selector, ops);     }          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();         }     }          private void sayHello(SocketChannel channel) throws Exception{         buffer.clear();         buffer.put("Hello 哈罗! \r\n".getBytes());         buffer.flip();         channel.write(buffer);     } }

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