org.argeo.eclipse.ui/src/org/argeo/eclipse/ui/jcr/AsyncUiEventListener.java

   1 /*
   2  * Copyright (C) 2007-2012 Argeo GmbH
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *         http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16 package org.argeo.eclipse.ui.jcr;
  17
  18 import java.util.ArrayList;
  19 import java.util.List;
  20
  21 import javax.jcr.RepositoryException;
  22 import javax.jcr.observation.Event;
  23 import javax.jcr.observation.EventIterator;
  24 import javax.jcr.observation.EventListener;
  25
  26 import org.apache.commons.logging.Log;
  27 import org.apache.commons.logging.LogFactory;
  28 import org.argeo.eclipse.ui.EclipseUiException;
  29 import org.eclipse.swt.widgets.Display;
  30
  31 /**
  32  * {@link EventListener} which simplifies running actions within the UI thread.
  33  */
  34 public abstract class AsyncUiEventListener implements EventListener {
  35         // private final static Log logSuper = LogFactory
  36         // .getLog(AsyncUiEventListener.class);
  37         private final Log logThis = LogFactory.getLog(getClass());
  38
  39         private final Display display;
  40
  41         public AsyncUiEventListener(Display display) {
  42                 super();
  43                 this.display = display;
  44         }
  45
  46         /** Called asynchronously in the UI thread. */
  47         protected abstract void onEventInUiThread(List<Event> events) throws RepositoryException;
  48
  49         /**
  50          * Whether these events should be processed in the UI or skipped with no UI
  51          * job created.
  52          */
  53         protected Boolean willProcessInUiThread(List<Event> events) throws RepositoryException {
  54                 return true;
  55         }
  56
  57         protected Log getLog() {
  58                 return logThis;
  59         }
  60
  61         public final void onEvent(final EventIterator eventIterator) {
  62                 final List<Event> events = new ArrayList<Event>();
  63                 while (eventIterator.hasNext())
  64                         events.add(eventIterator.nextEvent());
  65
  66                 if (logThis.isTraceEnabled())
  67                         logThis.trace("Received " + events.size() + " events");
  68
  69                 try {
  70                         if (!willProcessInUiThread(events))
  71                                 return;
  72                 } catch (RepositoryException e) {
  73                         throw new EclipseUiException("Cannot test skip events " + events, e);
  74                 }
  75
  76                 // Job job = new Job("JCR Events") {
  77                 // protected IStatus run(IProgressMonitor monitor) {
  78                 // if (display.isDisposed()) {
  79                 // logSuper.warn("Display is disposed cannot update UI");
  80                 // return Status.CANCEL_STATUS;
  81                 // }
  82
  83                 if (!display.isDisposed())
  84                         display.asyncExec(new Runnable() {
  85                                 public void run() {
  86                                         try {
  87                                                 onEventInUiThread(events);
  88                                         } catch (RepositoryException e) {
  89                                                 throw new EclipseUiException("Cannot process events " + events, e);
  90                                         }
  91                                 }
  92                         });
  93
  94                 // return Status.OK_STATUS;
  95                 // }
  96                 // };
  97                 // job.schedule();
  98         }
  99 }