Java example source code file (CustomQueryTest.java)

This example Java source code file (CustomQueryTest.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.

Learn more about this Java project at its project page.

Java - Java tags/keywords

assertionerror, atomicinteger, bytearrayoutputstream, count, countmbean, exception, failed, incrquery, malformedobjectnameexception, management, objectinputstream, objectname, objectoutputstream, queryeval, queryexp, util

The CustomQueryTest.java Java example source code

/*
 * Copyright (c) 2008, 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 6692027
 * @summary Check that custom subclasses of QueryEval can be serialized.
 * @author Eamonn McManus
 */

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.management.ManagementFactory;
import java.util.Set;
import java.util.concurrent.atomic.AtomicInteger;
import javax.management.MBeanServer;
import javax.management.MalformedObjectNameException;
import javax.management.ObjectName;
import javax.management.QueryEval;
import javax.management.QueryExp;

public class CustomQueryTest {
    public static interface CountMBean {
        public int getCount();
        public void increment();
    }

    public static class Count implements CountMBean {
        private AtomicInteger count = new AtomicInteger();

        public int getCount() {
            return count.get();
        }

        public void increment() {
            count.incrementAndGet();
        }

    }

    public static final ObjectName countName;
    static {
        try {
            countName = new ObjectName("d:type=Count");
        } catch (MalformedObjectNameException e) {
            throw new AssertionError(e);
        }
    }

    /* A query that calls the increment method of the Count MBean every time
     * it is evaluated.  If there is no ObjectName filter, the query will be
     * evaluated for every MBean in the MBean Server, so the count will be
     * incremented by the number of MBeans.
     */
    public static class IncrQuery extends QueryEval implements QueryExp {
        public boolean apply(ObjectName name) {
            try {
                getMBeanServer().invoke(countName, "increment", null, null);
                return true;
            } catch (Throwable t) {
                t.printStackTrace();
                System.exit(1);
                throw new AssertionError(); // not reached
            }
        }
    }

    public static void main(String[] args) throws Exception {
        MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
        mbs.registerMBean(new Count(), countName);
        int mbeanCount = mbs.getMBeanCount();
        QueryExp query = new IncrQuery();
        Set<ObjectName> names = mbs.queryNames(null, query);
        assertEquals(mbeanCount, names.size());
        assertEquals(mbeanCount, mbs.getAttribute(countName, "Count"));
        ByteArrayOutputStream bout = new ByteArrayOutputStream();
        ObjectOutputStream oout = new ObjectOutputStream(bout);
        oout.writeObject(query);
        oout.close();
        ByteArrayInputStream bin = new ByteArrayInputStream(bout.toByteArray());
        ObjectInputStream oin = new ObjectInputStream(bin);
        query = (QueryExp) oin.readObject();
        names = mbs.queryNames(null, query);
        assertEquals(mbeanCount * 2, mbs.getAttribute(countName, "Count"));
    }

    private static void assertEquals(Object expected, Object actual)
            throws Exception {
        if (!expected.equals(actual)) {
            String failure = "FAILED: expected " + expected + ", got " + actual;
            throw new Exception(failure);
        }
    }
}