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Java example source code file (GarbageCollectionNotificationTest.java)

This example Java source code file (GarbageCollectionNotificationTest.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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Java - Java tags/keywords

boolean, class, exception, field, garbagecollectionnotificationinfo, garbagecollectionnotificationtest, gclistener, hashmap, management, mbeanserver, object, objectname, privilegedaction, reflection, security, string, test, util

The GarbageCollectionNotificationTest.java Java example source code

/*
 * Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/*
 * @test
 * @bug     7036199
 * @summary Check that GarbageCollection notification are thrown by every GarbageCollectorMXBean
 * @author  Frederic Parain
 * @run     main/othervm GarbageCollectionNotificationTest
 */

import java.util.*;
import java.lang.management.*;
import java.lang.reflect.*;
import javax.management.*;
import javax.management.openmbean.*;
import com.sun.management.GarbageCollectionNotificationInfo;
import com.sun.management.GcInfo;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.lang.reflect.Field;

public class GarbageCollectionNotificationTest {
    private static HashMap<String,Boolean> listenerInvoked = new HashMap();
    static volatile long count = 0;
    static volatile long number = 0;
    static Object synchronizer = new Object();

    static class GcListener implements NotificationListener {
        public void handleNotification(Notification notif, Object handback) {
            String type = notif.getType();
            if (type.equals(GarbageCollectionNotificationInfo.GARBAGE_COLLECTION_NOTIFICATION)) {
                GarbageCollectionNotificationInfo gcNotif =
                    GarbageCollectionNotificationInfo.from((CompositeData) notif.getUserData());
                String source = ((ObjectName)notif.getSource()).getCanonicalName();
                synchronized(synchronizer) {
                    if(!listenerInvoked.get(source)) {
                            listenerInvoked.put(((ObjectName)notif.getSource()).getCanonicalName(),true);
                            count++;
                            if(count >= number) {
                                synchronizer.notify();
                            }
                    }
                }
            }
        }
    }

    public static void main(String[] args) throws Exception {
        MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
        final Boolean isNotificationSupported = AccessController.doPrivileged (new PrivilegedAction<Boolean>() {
                public Boolean run() {
                    try {
                        Class cl = Class.forName("sun.management.VMManagementImpl");
                        Field f = cl.getDeclaredField("gcNotificationSupport");
                        f.setAccessible(true);
                        return f.getBoolean(null);
                    } catch(ClassNotFoundException e) {
                        return false;
                    } catch(NoSuchFieldException e) {
                        return false;
                    } catch(IllegalAccessException e) {
                        return false;
                    }
                }
            });
        if(!isNotificationSupported) {
            System.out.println("GC Notification not supported by the JVM, test skipped");
            return;
        }
        final ObjectName gcMXBeanPattern =
                new ObjectName("java.lang:type=GarbageCollector,*");
        Set<ObjectName> names =
                mbs.queryNames(gcMXBeanPattern, null);
        if (names.isEmpty())
            throw new Exception("Test incorrect: no GC MXBeans");
        number = names.size();
        for (ObjectName n : names) {
            if(mbs.isInstanceOf(n,"javax.management.NotificationEmitter")) {
                listenerInvoked.put(n.getCanonicalName(),false);
                GcListener listener = new GcListener();
                mbs.addNotificationListener(n, listener, null, null);
            }
        }
        // Invocation of System.gc() to trigger major GC
        System.gc();
        // Allocation of many short living and small objects to trigger minor GC
        Object data[] = new Object[32];
        for(int i = 0; i<100000000; i++) {
            data[i%32] = new int[8];
        }
        int wakeup = 0;
        synchronized(synchronizer) {
            while(count != number) {
                synchronizer.wait(10000);
                wakeup++;
                if(wakeup > 10)
                    break;
            }
        }
        for (String source : listenerInvoked.keySet()) {
            if(!listenerInvoked.get(source))
                throw new Exception("Test incorrect: notifications have not been sent for "
                                    + source);
        }
        System.out.println("Test passed");
    }
}

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