Java NIO就緒模式怎么實現

這篇文章主要介紹“Java NIO就緒模式怎么實現”，在日常操作中，相信很多人在Java NIO就緒模式怎么實現問題上存在疑惑，小編查閱了各式資料，整理出簡單好用的操作方法，希望對大家解答”Java NIO就緒模式怎么實現”的疑惑有所幫助！接下來，請跟著小編一起來學習吧！

Java　NIO非堵塞應用通常適用用在I/O讀寫等方面，我們知道，系統運行的性能瓶頸通常在I/O讀寫，包括對端口和文件的操作上，過去，在打開一個I/O通道后，read()將一直等待在端口一邊讀取字節內容，如果沒有內容進來，read()也是傻傻的等，這會影響我們程序繼續做其他事情，那么改進做法就是開設線程，讓線程去等待，但是這樣做也是相當耗費資源的。

Java NIO非堵塞技術實際是采取Reactor模式，或者說是Observer模式為我們監察I/O端口，如果有內容進來，會自動通知我們，這樣，我們就不必開啟多個線程死等，從外界看，實現了流暢的I/O讀寫，不堵塞了。

Java NIO出現不只是一個技術性能的提高，你會發現網絡上到處在介紹它，因為它具有里程碑意義，從JDK1.4開始，Java開始提高性能相關的功能，從而使得Java在底層或者并行分布式計算等操作上已經可以和C或Perl等語言并駕齊驅。

圖 1      類結構圖

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: 使用線程池來處理大量channel并發  *   * @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);      /**      * 從socket中讀數據      */     protected void readDataFromSocket(SelectionKey key) throws Exception {         WorkerThread worker = pool.getWorker();         if (worker == null) {             return;         worker.serviceChannel(key);     }     /**      *        * @Project: concurrentnio      *      * @Author: chenkangxian      *      * @Annotation:線程池      *      * @Date:2011-7-20      *      * @Copyright: 2011 chenkangxian, All rights reserved.      *      */     private class ThreadPool {         List idle = new LinkedList();         /**          * 線程池初始化          *           * @param poolSize 線程池大小          */         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);             }         }         /**          * 獲得工作線程          *           * 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);         }         /**          * 送回工作線程          *           * 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;             //消除讀的關注             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;             }             //重新開始關注讀事件             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; /**  *   * @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(); //沒有輪詢，單個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上注冊channel，并設置interest      *       * Author: chenkangxian      *      * Last Modification Time: 2011-7-11      *      * @param selector 選擇器      *       * @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);     }     /**      * 處理有可用數據的通道      *       * Author: chenkangxian      *      * Last Modification Time: 2011-7-11      *      * @param key 可用通道對應的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 客戶端channel      *       * @throws Exception      */     private void sayHello(SocketChannel channel) throws Exception{         buffer.clear();         buffer.put("Hello 哈羅! \r\n".getBytes());         buffer.flip();         channel.write(buffer);     } }

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