bundles/org.simantics.browsing.ui.graph.impl/src/org/simantics/browsing/ui/graph/impl/LazyResourceQueryContainer.java

   1 /*******************************************************************************
   2  * Copyright (c) 2007, 2010 Association for Decentralized Information Management
   3  * in Industry THTH ry.
   4  * All rights reserved. This program and the accompanying materials
   5  * are made available under the terms of the Eclipse Public License v1.0
   6  * which accompanies this distribution, and is available at
   7  * http://www.eclipse.org/legal/epl-v10.html
   8  *
   9  * Contributors:
  10  *     VTT Technical Research Centre of Finland - initial API and implementation
  11  *******************************************************************************/
  12 package org.simantics.browsing.ui.graph.impl;
  13
  14 import org.simantics.browsing.ui.DataSource;
  15 import org.simantics.browsing.ui.NodeContext;
  16 import org.simantics.browsing.ui.NodeContext.PrimitiveQueryKey;
  17 import org.simantics.browsing.ui.PrimitiveQueryProcessor;
  18 import org.simantics.browsing.ui.PrimitiveQueryUpdater;
  19 import org.simantics.browsing.ui.graph.impl.request.ResourceQuery;
  20 import org.simantics.db.AsyncReadGraph;
  21 import org.simantics.db.ReadGraph;
  22 import org.simantics.db.exception.DatabaseException;
  23 import org.simantics.db.procedure.Listener;
  24 import org.simantics.utils.Container;
  25
  26 public abstract class LazyResourceQueryContainer<Result> implements Container<Result> {
  27
  28     final private ResourceQuery<Result> query;
  29
  30     final private PrimitiveQueryUpdater updater;
  31
  32     private final Listener<Result> procedure;
  33
  34     final protected NodeContext        context;
  35
  36     private Result                      result;
  37
  38     private boolean                     computed = false;
  39
  40     /**
  41      * Computes the graph query result. This will get called asynchronously.
  42      *
  43      * @param graph
  44      * @return
  45      */
  46     protected abstract Result compute(ReadGraph graph) throws DatabaseException;
  47
  48     /**
  49      * Needed for retrieving the actual primitive query key that is used to with
  50      * {@link PrimitiveQueryUpdater#scheduleReplace(NodeContext, PrimitiveQueryKey, Object)}
  51      * inside the {@link #query} that is initialized in the constructor
  52      * {@link #LazyResourceQueryContainer(PrimitiveQueryUpdater, NodeContext, Object, Object)}
  53      * .
  54      *
  55      * <p>
  56      * This key should originally be received by the actual
  57      * {@link PrimitiveQueryProcessor} that has been invoked to compute the
  58      * result that will be stored in this {@link LazyResourceQueryContainer}.
  59      *
  60      * @return
  61      */
  62     protected abstract PrimitiveQueryKey<Container<Result>> getKey();
  63
  64     public LazyResourceQueryContainer(final PrimitiveQueryUpdater updater, final NodeContext context, Result initial) {
  65
  66         this.updater = updater;
  67         this.context = context;
  68         this.result = initial;
  69
  70         this.query = new ResourceQuery<Result>(getKey(), context) {
  71
  72             @Override
  73             public Result perform(ReadGraph graph) throws DatabaseException {
  74                 return compute(graph);
  75             }
  76
  77         };
  78
  79         procedure = new Listener<Result>() {
  80
  81             @Override
  82             public void execute(Result result) {
  83                 setResult(result);
  84                 updater.scheduleReplace(context, getKey(), LazyResourceQueryContainer.this);
  85             }
  86
  87             @Override
  88             public boolean isDisposed() {
  89                 return updater.isDisposed();
  90             }
  91
  92             public void exception(Throwable t) {
  93                 System.out.print("LazyResourceQueryContainer2.request failed: ");
  94                 t.printStackTrace();
  95             }
  96
  97         };
  98
  99     }
 100
 101     protected PrimitiveQueryUpdater getUpdater() {
 102         return updater;
 103     }
 104
 105     private void setResult(Result result) {
 106         this.result = result;
 107         computed = true;
 108     }
 109
 110     @Override
 111     public Result get() {
 112
 113         if (!computed) {
 114
 115             final DataSource<AsyncReadGraph> source = updater.getDataSource(AsyncReadGraph.class);
 116             assert(source != null);
 117
 118             source.schedule(graph -> graph.asyncRequest(query, procedure));
 119
 120         }
 121
 122         return result;
 123
 124     }
 125
 126 }