org.eclipse.linuxtools.tmf/src/org/eclipse/linuxtools/tmf/request/TmfRequestExecutor.java

   1 /*******************************************************************************
   2  * Copyright (c) 2009, 2010 Ericsson
   3  *
   4  * All rights reserved. This program and the accompanying materials are
   5  * made available under the terms of the Eclipse Public License v1.0 which
   6  * accompanies this distribution, and is available at
   7  * http://www.eclipse.org/legal/epl-v10.html
   8  *
   9  * Contributors:
  10  *   Francois Chouinard - Initial API and implementation
  11  *******************************************************************************/
  12
  13 package org.eclipse.linuxtools.tmf.request;
  14
  15 import java.util.Queue;
  16 import java.util.concurrent.Executor;
  17 import java.util.concurrent.ExecutorService;
  18 import java.util.concurrent.Executors;
  19 import java.util.concurrent.LinkedBlockingQueue;
  20
  21 /**
  22  * <b><u>TmfRequestExecutor</u></b>
  23  *
  24  * A simple, straightforward request executor.
  25  */
  26 public class TmfRequestExecutor implements Executor {
  27
  28         private final ExecutorService fExecutor;
  29         private final String fExecutorName;
  30         private final Queue<Runnable> fRequestQueue = new LinkedBlockingQueue<Runnable>();
  31         private Runnable fCurrentRequest;
  32
  33         // ------------------------------------------------------------------------
  34         // Constructors
  35         // ------------------------------------------------------------------------
  36
  37         public TmfRequestExecutor() {
  38                 this(Executors.newSingleThreadExecutor());
  39         }
  40
  41         public TmfRequestExecutor(ExecutorService executor) {
  42                 fExecutor = executor;
  43                 String canonicalName = fExecutor.getClass().getCanonicalName();
  44                 fExecutorName = canonicalName.substring(canonicalName.lastIndexOf('.') + 1);
  45         }
  46
  47         /**
  48          * @return the number of pending requests
  49          */
  50         public int getNbPendingRequests() {
  51                 return fRequestQueue.size();
  52         }
  53
  54         /**
  55          * @return the shutdown state (i.e. if it is accepting new requests)
  56          */
  57         public boolean isShutdown() {
  58                 return fExecutor.isShutdown();
  59         }
  60
  61         /**
  62          * @return the termination state
  63          */
  64         public boolean isTerminated() {
  65                 return fExecutor.isTerminated();
  66         }
  67
  68         /**
  69          * Stops the executor
  70          */
  71         public void stop() {
  72                 fExecutor.shutdown();
  73         }
  74
  75         // ------------------------------------------------------------------------
  76         // Operations
  77         // ------------------------------------------------------------------------
  78
  79         /* (non-Javadoc)
  80          * @see java.util.concurrent.Executor#execute(java.lang.Runnable)
  81          */
  82         public synchronized void execute(final Runnable request) {
  83                 fRequestQueue.offer(new Runnable() {
  84                         public void run() {
  85                                 try {
  86                                         request.run();
  87                                 } finally {
  88                                         scheduleNext();
  89                                 }
  90                         }
  91                 });
  92                 if (fCurrentRequest == null) {
  93                         scheduleNext();
  94                 }
  95         }
  96
  97         /**
  98          * Executes the next pending request, if applicable.
  99          */
 100         protected synchronized void scheduleNext() {
 101                 if ((fCurrentRequest = fRequestQueue.poll()) != null) {
 102                         fExecutor.execute(fCurrentRequest);
 103                 }
 104         }
 105
 106         // ------------------------------------------------------------------------
 107         // Object
 108         // ------------------------------------------------------------------------
 109
 110         @Override
 111         public String toString() {
 112                 return "[TmfRequestExecutor(" + fExecutorName + ")]";
 113         }
 114
 115 }