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