bundles/org.simantics.db.common/src/org/simantics/db/common/procedure/single/wrapper/SingleOrNullProcedure.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.db.common.procedure.single.wrapper;
  13
  14 import java.util.concurrent.atomic.AtomicBoolean;
  15
  16 import org.simantics.db.AsyncReadGraph;
  17 import org.simantics.db.common.procedure.adapter.AsyncMultiProcedureAdapter;
  18 import org.simantics.db.common.utils.Logger;
  19 import org.simantics.db.procedure.AsyncProcedure;
  20
  21 final public class SingleOrNullProcedure<Result> extends AsyncMultiProcedureAdapter<Result> {
  22
  23         private Result result = null;
  24         final AsyncProcedure<Result> procedure;
  25     final AtomicBoolean found = new AtomicBoolean(false);
  26     final AtomicBoolean done = new AtomicBoolean(false);
  27
  28     public SingleOrNullProcedure(AsyncProcedure<Result> procedure) {
  29         this.procedure = procedure;
  30     }
  31
  32     @Override
  33     public void finished(AsyncReadGraph graph) {
  34
  35         // Shall fire exactly once!
  36         if(done.compareAndSet(false, true)) {
  37                 try {
  38                         procedure.execute(graph, result);
  39                 } catch (Throwable t) {
  40                         Logger.defaultLogError(t);
  41                 }
  42         }
  43
  44     }
  45
  46     @Override
  47     public void execute(AsyncReadGraph graph, Result result) {
  48
  49                 if(found.compareAndSet(false, true)) {
  50                         this.result = result;
  51                 } else {
  52                         // Shall fire exactly once!
  53                         if(done.compareAndSet(false, true)) {
  54                                 try {
  55                                 procedure.execute(graph, null);
  56                                 } catch (Throwable t) {
  57                                 Logger.defaultLogError(t);
  58                                 }
  59                         }
  60                 }
  61
  62     }
  63
  64
  65     @Override
  66     public void exception(AsyncReadGraph graph, Throwable t) {
  67                 // Shall fire exactly once!
  68                 if(done.compareAndSet(false, true)) {
  69                         try {
  70                                 procedure.exception(graph, t);
  71                         } catch (Throwable t2) {
  72                         Logger.defaultLogError(t2);
  73                         }
  74                 }
  75     }
  76
  77     @Override
  78     public String toString() {
  79         return "SingleOrNullProcedure -> " + procedure;
  80     }
  81
  82 }