bundles/org.simantics.db.common/src/org/simantics/db/common/procedure/single/wrapper/SingleOrNullProcedure.java

   1 /*******************************************************************************\r
   2  * Copyright (c) 2007, 2010 Association for Decentralized Information Management\r
   3  * in Industry THTH ry.\r
   4  * All rights reserved. This program and the accompanying materials\r
   5  * are made available under the terms of the Eclipse Public License v1.0\r
   6  * which accompanies this distribution, and is available at\r
   7  * http://www.eclipse.org/legal/epl-v10.html\r
   8  *\r
   9  * Contributors:\r
  10  *     VTT Technical Research Centre of Finland - initial API and implementation\r
  11  *******************************************************************************/\r
  12 package org.simantics.db.common.procedure.single.wrapper;\r
  13 \r
  14 import java.util.concurrent.atomic.AtomicBoolean;\r
  15 \r
  16 import org.simantics.db.AsyncReadGraph;\r
  17 import org.simantics.db.common.procedure.adapter.AsyncMultiProcedureAdapter;\r
  18 import org.simantics.db.common.utils.Logger;\r
  19 import org.simantics.db.procedure.AsyncProcedure;\r
  20 \r
  21 final public class SingleOrNullProcedure<Result> extends AsyncMultiProcedureAdapter<Result> {\r
  22     \r
  23         private Result result = null;\r
  24         final AsyncProcedure<Result> procedure;\r
  25     final AtomicBoolean found = new AtomicBoolean(false);\r
  26     final AtomicBoolean done = new AtomicBoolean(false);\r
  27     \r
  28     public SingleOrNullProcedure(AsyncProcedure<Result> procedure) {\r
  29         this.procedure = procedure;\r
  30     }\r
  31     \r
  32     @Override\r
  33     public void finished(AsyncReadGraph graph) {\r
  34 \r
  35         // Shall fire exactly once!\r
  36         if(done.compareAndSet(false, true)) {\r
  37                 try {\r
  38                         procedure.execute(graph, result);\r
  39                 } catch (Throwable t) {\r
  40                         Logger.defaultLogError(t);\r
  41                 }\r
  42         }\r
  43         \r
  44     }\r
  45 \r
  46     @Override\r
  47     public void execute(AsyncReadGraph graph, Result result) {\r
  48         \r
  49                 if(found.compareAndSet(false, true)) {\r
  50                         this.result = result;\r
  51                 } else {\r
  52                         // Shall fire exactly once!\r
  53                         if(done.compareAndSet(false, true)) {\r
  54                                 try {\r
  55                                 procedure.execute(graph, null);\r
  56                                 } catch (Throwable t) {\r
  57                                 Logger.defaultLogError(t);\r
  58                                 }\r
  59                         }\r
  60                 }\r
  61         \r
  62     }\r
  63         \r
  64     \r
  65     @Override\r
  66     public void exception(AsyncReadGraph graph, Throwable t) {\r
  67                 // Shall fire exactly once!\r
  68                 if(done.compareAndSet(false, true)) {\r
  69                         try {\r
  70                                 procedure.exception(graph, t);\r
  71                         } catch (Throwable t2) {\r
  72                         Logger.defaultLogError(t2);\r
  73                         }\r
  74                 }\r
  75     }\r
  76     \r
  77     @Override\r
  78     public String toString() {\r
  79         return "SingleOrNullProcedure -> " + procedure;\r
  80     }\r
  81 \r
  82 }\r