--- /dev/null
+/*******************************************************************************\r
+ * Copyright (c) 2007, 2010 Association for Decentralized Information Management\r
+ * in Industry THTH ry.\r
+ * All rights reserved. This program and the accompanying materials\r
+ * are made available under the terms of the Eclipse Public License v1.0\r
+ * which accompanies this distribution, and is available at\r
+ * http://www.eclipse.org/legal/epl-v10.html\r
+ *\r
+ * Contributors:\r
+ * VTT Technical Research Centre of Finland - initial API and implementation\r
+ *******************************************************************************/\r
+package org.simantics.db.common.procedure.guarded;\r
+\r
+import java.util.concurrent.atomic.AtomicBoolean;\r
+import java.util.concurrent.atomic.AtomicInteger;\r
+\r
+import org.simantics.db.AsyncReadGraph;\r
+import org.simantics.db.common.procedure.adapter.AsyncProcedureAdapter;\r
+import org.simantics.db.procedure.AsyncProcedure;\r
+import org.simantics.db.procedure.Procedure;\r
+\r
+/**\r
+ * An asynchronous database callback procedure that is guarded against multiple\r
+ * invocations to {@link Procedure#execute(Object)} and\r
+ * {@link Procedure#exception(Throwable)}. Only the first invocation of is\r
+ * delegated or the Nth invocation to {@link Procedure#execute(Object)} where\r
+ * Nth is <code>expectedResults</code>.\r
+ * \r
+ * @author Tuukka Lehtonen\r
+ * \r
+ * @param <T>\r
+ */\r
+public class GuardedAsyncProcedureWrapper<T> extends AsyncProcedureAdapter<T> {\r
+\r
+ private final AsyncProcedure<T> procedure;\r
+ private final AtomicBoolean onceGuard = new AtomicBoolean(false);\r
+ private final AtomicInteger resultCounter;\r
+\r
+ public GuardedAsyncProcedureWrapper(AsyncProcedure<T> procedure, int expectedResults) {\r
+ this.procedure = procedure;\r
+ this.resultCounter = new AtomicInteger(expectedResults);\r
+ }\r
+\r
+ @Override\r
+ public void exception(AsyncReadGraph graph, Throwable t) {\r
+ if (onceGuard.compareAndSet(false, true)) {\r
+ procedure.exception(graph, t);\r
+ }\r
+ }\r
+\r
+ @Override\r
+ public void execute(AsyncReadGraph graph, T result) {\r
+ int count = resultCounter.decrementAndGet();\r
+ if (count == 0) {\r
+ if (onceGuard.compareAndSet(false, true)) {\r
+ procedure.execute(graph, result);\r
+ }\r
+ } else if (count < 0) {\r
+ System.out.println(this + ": execute invoked more than expected (count=" + count + ", procedure=" + procedure + ")");\r
+ }\r
+ }\r
+\r
+}\r