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 java.util.function.Consumer;
  15
  16 import org.simantics.browsing.ui.DataSource;
  17 import org.simantics.browsing.ui.NodeContext;
  18 import org.simantics.browsing.ui.NodeContext.PrimitiveQueryKey;
  19 import org.simantics.browsing.ui.PrimitiveQueryProcessor;
  20 import org.simantics.browsing.ui.PrimitiveQueryUpdater;
  21 import org.simantics.browsing.ui.graph.impl.request.ResourceQuery;
  22 import org.simantics.db.ReadGraph;
  23 import org.simantics.db.exception.DatabaseException;
  24 import org.simantics.db.procedure.Listener;
  25 import org.simantics.utils.Container;
  26
  27 public abstract class LazyResourceQueryContainer<Result> implements Container<Result> {
  28
  29     final private ResourceQuery<Result> query;
  30
  31     final private PrimitiveQueryUpdater updater;
  32
  33     private final Listener<Result> procedure;
  34
  35     final protected NodeContext        context;
  36
  37     private Result                      result;
  38
  39     private boolean                     computed = false;
  40
  41     /**
  42      * Computes the graph query result. This will get called asynchronously.
  43      *
  44      * @param graph
  45      * @return
  46      */
  47     protected abstract Result compute(ReadGraph graph) throws DatabaseException;
  48
  49     /**
  50      * Needed for retrieving the actual primitive query key that is used to with
  51      * {@link PrimitiveQueryUpdater#scheduleReplace(NodeContext, PrimitiveQueryKey, Object)}
  52      * inside the {@link #query} that is initialized in the constructor
  53      * {@link #LazyResourceQueryContainer(PrimitiveQueryUpdater, NodeContext, Object, Object)}
  54      * .
  55      *
  56      * <p>
  57      * This key should originally be received by the actual
  58      * {@link PrimitiveQueryProcessor} that has been invoked to compute the
  59      * result that will be stored in this {@link LazyResourceQueryContainer}.
  60      *
  61      * @return
  62      */
  63     protected abstract PrimitiveQueryKey<Container<Result>> getKey();
  64
  65     public LazyResourceQueryContainer(final PrimitiveQueryUpdater updater, final NodeContext context, Result initial) {
  66
  67         this.updater = updater;
  68         this.context = context;
  69         this.result = initial;
  70
  71         this.query = new ResourceQuery<Result>(getKey(), context) {
  72
  73             @Override
  74             public Result perform(ReadGraph graph) throws DatabaseException {
  75                 return compute(graph);
  76             }
  77
  78         };
  79
  80         procedure = new Listener<Result>() {
  81
  82             @Override
  83             public void execute(Result result) {
  84                 setResult(result);
  85                 updater.scheduleReplace(context, getKey(), LazyResourceQueryContainer.this);
  86             }
  87
  88             @Override
  89             public boolean isDisposed() {
  90                 return updater.isDisposed();
  91             }
  92
  93             public void exception(Throwable t) {
  94                 System.out.print("LazyResourceQueryContainer2.request failed: ");
  95                 t.printStackTrace();
  96             }
  97
  98         };
  99
 100     }
 101
 102     protected PrimitiveQueryUpdater getUpdater() {
 103         return updater;
 104     }
 105
 106     private void setResult(Result result) {
 107         this.result = result;
 108         computed = true;
 109     }
 110
 111     @Override
 112     public Result get() {
 113
 114         if (!computed) {
 115
 116             final DataSource<ReadGraph> source = updater.getDataSource(ReadGraph.class);
 117             assert(source != null);
 118
 119             source.schedule(new Consumer<ReadGraph>() {
 120
 121                 @Override
 122                 public void accept(ReadGraph source) {
 123
 124                     source.asyncRequest(query, procedure);
 125
 126                 }
 127
 128             });
 129
 130         }
 131
 132         return result;
 133
 134     }
 135
 136 }