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    1   /*
    2    * Copyright (c) 1996, Oracle and/or its affiliates. All rights reserved.
    3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
    4    *
    5    * This code is free software; you can redistribute it and/or modify it
    6    * under the terms of the GNU General Public License version 2 only, as
    7    * published by the Free Software Foundation.  Oracle designates this
    8    * particular file as subject to the "Classpath" exception as provided
    9    * by Oracle in the LICENSE file that accompanied this code.
   10    *
   11    * This code is distributed in the hope that it will be useful, but WITHOUT
   12    * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   13    * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   14    * version 2 for more details (a copy is included in the LICENSE file that
   15    * accompanied this code).
   16    *
   17    * You should have received a copy of the GNU General Public License version
   18    * 2 along with this work; if not, write to the Free Software Foundation,
   19    * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   20    *
   21    * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   22    * or visit www.oracle.com if you need additional information or have any
   23    * questions.
   24    */
   25   
   26   package sun.misc;
   27   
   28   /**
   29    * The request processor allows functors (Request instances) to be created
   30    * in arbitrary threads, and to be posted for execution in a non-restricted
   31    * thread.
   32    *
   33    * @author      Steven B. Byrne
   34    */
   35   
   36   
   37   public class RequestProcessor implements Runnable {
   38   
   39       private static Queue requestQueue;
   40       private static Thread dispatcher;
   41   
   42       /**
   43        * Queues a Request instance for execution by the request procesor
   44        * thread.
   45        */
   46       public static void postRequest(Request req) {
   47           lazyInitialize();
   48           requestQueue.enqueue(req);
   49       }
   50   
   51       /**
   52        * Process requests as they are queued.
   53        */
   54       public void run() {
   55           lazyInitialize();
   56           while (true) {
   57               try {
   58                   Object obj = requestQueue.dequeue();
   59                   if (obj instanceof Request) { // ignore bogons
   60                       Request req = (Request)obj;
   61                       try {
   62                           req.execute();
   63                       } catch (Throwable t) {
   64                           // do nothing at the moment...maybe report an error
   65                           // in the future
   66                       }
   67                   }
   68               } catch (InterruptedException e) {
   69                   // do nothing at the present time.
   70               }
   71           }
   72       }
   73   
   74   
   75       /**
   76        * This method initiates the request processor thread.  It is safe
   77        * to call it after the thread has been started.  It provides a way for
   78        * clients to deliberately control the context in which the request
   79        * processor thread is created
   80        */
   81       public static synchronized void startProcessing() {
   82           if (dispatcher == null) {
   83               dispatcher = new Thread(new RequestProcessor(), "Request Processor");
   84               dispatcher.setPriority(Thread.NORM_PRIORITY + 2);
   85               dispatcher.start();
   86           }
   87       }
   88   
   89   
   90       /**
   91        * This method performs lazy initialization.
   92        */
   93       private static synchronized void lazyInitialize() {
   94           if (requestQueue == null) {
   95               requestQueue = new Queue();
   96           }
   97       }
   98   
   99   }

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