artemis-commons/src/main/java/org/apache/activemq/artemis/utils/actors/HandlerBase.java

/*
 * 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;
   }

   /** 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<Counter> inHandler = ThreadLocal.withInitial(() -> new Counter());

   protected static void enter() {
      inHandler.get().count++;
   }

   public static boolean inHandler() {
      return inHandler.get().count > 0;
   }

   protected static void leave() {
      inHandler.get().count--;
   }

}