All Downloads are FREE. Search and download functionalities are using the official Maven repository.

org.glassfish.common.util.InstanceCounter Maven / Gradle / Ivy

There is a newer version: 7.2024.1.Alpha1
Show newest version
/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright (c) [2020] Payara Foundation and/or its affiliates. All rights reserved.
 *
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License.  You can
 * obtain a copy of the License at
 * https://github.com/payara/Payara/blob/master/LICENSE.txt
 * See the License for the specific
 * language governing permissions and limitations under the License.
 *
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at glassfish/legal/LICENSE.txt.
 *
 * GPL Classpath Exception:
 * The Payara Foundation designates this particular file as subject to the "Classpath"
 * exception as provided by the Payara Foundation in the GPL Version 2 section of the License
 * file that accompanied this code.
 *
 * Modifications:
 * If applicable, add the following below the License Header, with the fields
 * enclosed by brackets [] replaced by your own identifying information:
 * "Portions Copyright [year] [name of copyright owner]"
 *
 * Contributor(s):
 * If you wish your version of this file to be governed by only the CDDL or
 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
 * only if the new code is made subject to such option by the copyright
 * holder.
 */
package org.glassfish.common.util;

import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.util.Collections;
import java.util.IdentityHashMap;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

/**
 * Counts instances of a particular class, helpful in leak detection
 * 

* Example: Put the following line into the class you want counted: *

* {@code * private final InstanceCounter instanceCounter = new InstanceCounter<>(this); * } * * @author Cuba Stanley */ public class InstanceCounter { private static class Count { int instanceCount; private final ReferenceQueue referenceQueue = new ReferenceQueue<>(); private final Set> references = Collections.newSetFromMap(new IdentityHashMap<>()); public Count() { instanceCount = 1; } public Count(int instanceCount) { this.instanceCount = instanceCount; } } private static final ConcurrentMap, Count> INSTANCE_COUNT = new ConcurrentHashMap<>(); /** * triggers instance counting of the specified * * @param counted object to be counted */ public InstanceCounter(Object counted) { INSTANCE_COUNT.compute(counted.getClass(), (clazz, value) -> { Count count; if (value == null) { count = new Count(); } else { count = value; ++count.instanceCount; } count.references.add(new WeakReference<>(counted, count.referenceQueue)); return count; }); } /** * Returns instance count of a particular class. * * @param countedType * @param timeout in milliseconds to wait to collect removed instances * @return current instance count */ public static int getInstanceCount(Class countedType, long timeout) { INSTANCE_COUNT.compute(countedType, (clazz, value) -> { if (value == null) { return new Count(0); } else { try { value.instanceCount -= countRemovedInstances(value, timeout); } catch (InterruptedException ex) { throw new RuntimeException(ex); } return value; } }); return INSTANCE_COUNT.get(countedType).instanceCount; } /** * gets actual references to counted objects * * @param countedType * @param timeout in milliseconds * @return list of counted objects */ public static Set> getInstances(Class countedType, long timeout) { getInstanceCount(countedType, timeout); // update the count, create if necessary return INSTANCE_COUNT.get(countedType).references; } private static int countRemovedInstances(Count count, long timeout) throws InterruptedException { int removedInstances = 0; Reference reference = count.referenceQueue.remove(timeout); while (reference != null) { ++removedInstances; reference.clear(); assert count.references.remove(reference) : "non-existent reference"; reference = count.referenceQueue.poll(); } return removedInstances; } }