org.apache.activemq.artemis.utils.AutomaticLatch Maven / Gradle / Ivy
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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including
all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and
JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up
with different versions on classes on the class path).
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.activemq.artemis.utils;
/** An automatic latch has the same semantic as the ReusableLatch
* However this class has a replaceable callback that could be called
* when the number of elements reach zero.
* With that you can either block to wait completion, or to send a callback to be
* used when it reaches 0. */
public class AutomaticLatch extends AbstractLatch {
volatile Runnable afterCompletion;
public AutomaticLatch() {
}
public AutomaticLatch(int count) {
super(count);
}
// it will execute when the counter reaches 0.
// notice that since the latch is reusable,
// the runnable will be cleared once it reached 0
public void afterCompletion(final Runnable newRun) {
// We first raise one element up
// to avoid a race on it being called while another thread sets it down to 0
countUp();
if (this.afterCompletion != null) {
// this should not happen really,
// but just in case it ever happens,
// I would rather have a runnable depending into other runnables instead of a collection here
// as the use case I'm after is a single runnable
final Runnable oldRun = afterCompletion;
this.afterCompletion = () -> {
oldRun.run();
newRun.run();
};
} else {
this.afterCompletion = newRun;
}
// then we countDown so it will be instantly 0 if nothing else done it
// or it then just keep flow as usual
countDown();
}
@Override
public final void countDown() {
if (control.releaseShared(1)) {
doRun();
}
}
private void doRun() {
Runnable toRun = afterCompletion;
afterCompletion = null;
if (toRun != null) {
toRun.run();
}
}
@Override
public final void countDown(final int count) {
if (control.releaseShared(count)) {
doRun();
}
}
}