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/*
* 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.actors;
/**
* This abstract class will encapsulate
* ThreadLocals to determine when a class is a handler.
* This is because some functionality has to be avoided if inHandler().
*
*/
public abstract class HandlerBase {
private static class Counter {
int count = 0;
}
// There is only going to be a single Thread using the counter, so it is safe to cache this instance
private final Counter cachedCounter = new Counter();
/** an actor could be used within an OrderedExecutor. So we need this counter to decide if there's a Handler anywhere in the stack trace */
private static final ThreadLocal counterThreadLocal = new ThreadLocal<>();
protected void enter() {
Counter counter = counterThreadLocal.get();
if (counter == null) {
cachedCounter.count = 1;
counterThreadLocal.set(cachedCounter);
} else {
counter.count++;
}
}
public boolean inHandler() {
Counter counter = counterThreadLocal.get();
if (counter == null) {
return false;
} else if (counter.count == 0) {
counterThreadLocal.remove();
}
return counter.count > 0;
}
protected void leave() {
Counter counter = counterThreadLocal.get();
if (counter != null && --counter.count <= 0) {
counterThreadLocal.remove();
}
}
}