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 import org.eclipse.linuxtools.tmf.Tracer;
  22
  23 /**
  24  * <b><u>TmfRequestExecutor</u></b>
  25  *
  26  * A simple, straightforward request executor.
  27  */
  28 public class TmfRequestExecutor implements Executor {
  29
  30         private final ExecutorService fExecutor;
  31         private final String fExecutorName;
  32         private final Queue<Runnable> fRequestQueue = new LinkedBlockingQueue<Runnable>();
  33         private Runnable fCurrentRequest;
  34
  35         // ------------------------------------------------------------------------
  36         // Constructors
  37         // ------------------------------------------------------------------------
  38
  39         public TmfRequestExecutor() {
  40                 this(Executors.newSingleThreadExecutor());
  41         }
  42
  43         public TmfRequestExecutor(ExecutorService executor) {
  44                 fExecutor = executor;
  45                 String canonicalName = fExecutor.getClass().getCanonicalName();
  46                 fExecutorName = canonicalName.substring(canonicalName.lastIndexOf('.') + 1);
  47                 Tracer.trace(fExecutor + " created");
  48         }
  49
  50         /**
  51          * @return the number of pending requests
  52          */
  53         public int getNbPendingRequests() {
  54                 return fRequestQueue.size();
  55         }
  56
  57         /**
  58          * @return the shutdown state (i.e. if it is accepting new requests)
  59          */
  60         public boolean isShutdown() {
  61                 return fExecutor.isShutdown();
  62         }
  63
  64         /**
  65          * @return the termination state
  66          */
  67         public boolean isTerminated() {
  68                 return fExecutor.isTerminated();
  69         }
  70
  71         /**
  72          * Stops the executor
  73          */
  74         public void stop() {
  75                 fExecutor.shutdown();
  76                 Tracer.trace(fExecutor + " terminated");
  77         }
  78
  79         // ------------------------------------------------------------------------
  80         // Operations
  81         // ------------------------------------------------------------------------
  82
  83         /* (non-Javadoc)
  84          * @see java.util.concurrent.Executor#execute(java.lang.Runnable)
  85          */
  86         public synchronized void execute(final Runnable request) {
  87                 Tracer.trace("Queueing request " + request);
  88                 fRequestQueue.offer(new Runnable() {
  89                         public void run() {
  90                                 try {
  91                                         Tracer.trace("Processing request " + request);
  92                                         request.run();
  93                                         Tracer.trace("Finishing request " + request);
  94                                 } finally {
  95                                         scheduleNext();
  96                                 }
  97                         }
  98                 });
  99                 if (fCurrentRequest == null) {
 100                         scheduleNext();
 101                 }
 102         }
 103
 104         /**
 105          * Executes the next pending request, if applicable.
 106          */
 107         protected synchronized void scheduleNext() {
 108                 if ((fCurrentRequest = fRequestQueue.poll()) != null) {
 109                         fExecutor.execute(fCurrentRequest);
 110                 }
 111         }
 112
 113         // ------------------------------------------------------------------------
 114         // Object
 115         // ------------------------------------------------------------------------
 116
 117         @Override
 118         public String toString() {
 119                 return "[TmfRequestExecutor(" + fExecutorName + ")]";
 120         }
 121
 122 }