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 //              if (Tracer.COMPONENTS) Tracer.trace(fExecutor + " created");
  46         }
  47
  48         /**
  49          * @return the number of pending requests
  50          */
  51         public int getNbPendingRequests() {
  52                 return fRequestQueue.size();
  53         }
  54
  55         /**
  56          * @return the shutdown state (i.e. if it is accepting new requests)
  57          */
  58         public boolean isShutdown() {
  59                 return fExecutor.isShutdown();
  60         }
  61
  62         /**
  63          * @return the termination state
  64          */
  65         public boolean isTerminated() {
  66                 return fExecutor.isTerminated();
  67         }
  68
  69         /**
  70          * Stops the executor
  71          */
  72         public void stop() {
  73                 fExecutor.shutdown();
  74 //              if (Tracer.COMPONENTS) Tracer.trace(fExecutor + " terminated");
  75         }
  76
  77         // ------------------------------------------------------------------------
  78         // Operations
  79         // ------------------------------------------------------------------------
  80
  81         /* (non-Javadoc)
  82          * @see java.util.concurrent.Executor#execute(java.lang.Runnable)
  83          */
  84         public synchronized void execute(final Runnable request) {
  85                 fRequestQueue.offer(new Runnable() {
  86                         public void run() {
  87                                 try {
  88                                         request.run();
  89                                 } finally {
  90                                         scheduleNext();
  91                                 }
  92                         }
  93                 });
  94                 if (fCurrentRequest == null) {
  95                         scheduleNext();
  96                 }
  97         }
  98
  99         /**
 100          * Executes the next pending request, if applicable.
 101          */
 102         protected synchronized void scheduleNext() {
 103                 if ((fCurrentRequest = fRequestQueue.poll()) != null) {
 104                         fExecutor.execute(fCurrentRequest);
 105                 }
 106         }
 107
 108         // ------------------------------------------------------------------------
 109         // Object
 110         // ------------------------------------------------------------------------
 111
 112         @Override
 113         public String toString() {
 114                 return "[TmfRequestExecutor(" + fExecutorName + ")]";
 115         }
 116
 117 }