Java example source code file (InstanceOfQueryExp.java)

This example Java source code file (InstanceOfQueryExp.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

badattributevalueexpexception, badbinaryopvalueexpexception, badstringoperationexception, classcastexception, illegalargumentexception, instancenotfoundexception, instanceofqueryexp, invalidapplicationexception, null, queryeval, stringvalueexp

The InstanceOfQueryExp.java Java example source code

/*
 * Copyright (c) 2005, 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * 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.
 */

package javax.management;


/**
 * This class is used by the query building mechanism for isInstanceOf expressions.
 * @serial include
 *
 * @since 1.6
 */
class InstanceOfQueryExp extends QueryEval implements QueryExp {

    /* Serial version */
    private static final long serialVersionUID = -1081892073854801359L;

    /**
     * @serial The {@link StringValueExp} returning the name of the class
     *         of which selected MBeans should be instances.
     */
    private StringValueExp classNameValue;

    /**
     * Creates a new InstanceOfExp with a specific class name.
     * @param classNameValue The {@link StringValueExp} returning the name of
     *        the class of which selected MBeans should be instances.
     */
    // We are using StringValueExp here to be consistent with other queries,
    // although we should actually either use a simple string (the classname)
    // or a ValueExp - which would allow more complex queries - like for
    // instance evaluating the class name from an AttributeValueExp.
    // As it stands - using StringValueExp instead of a simple constant string
    // doesn't serve any useful purpose besides offering a consistent
    // look & feel.
    public InstanceOfQueryExp(StringValueExp classNameValue) {
        if (classNameValue == null) {
            throw new IllegalArgumentException("Null class name.");
        }

        this.classNameValue = classNameValue;
    }

    /**
     * Returns the class name.
     * @returns The {@link StringValueExp} returning the name of
     *        the class of which selected MBeans should be instances.
     */
    public StringValueExp getClassNameValue()  {
        return classNameValue;
    }

    /**
     * Applies the InstanceOf on a MBean.
     *
     * @param name The name of the MBean on which the InstanceOf will be applied.
     *
     * @return  True if the MBean specified by the name is instance of the class.
     * @exception BadAttributeValueExpException
     * @exception InvalidApplicationException
     * @exception BadStringOperationException
     * @exception BadBinaryOpValueExpException
     */
    public boolean apply(ObjectName name)
        throws BadStringOperationException,
        BadBinaryOpValueExpException,
        BadAttributeValueExpException,
        InvalidApplicationException {

        // Get the class name value
        final StringValueExp val;
        try {
            val = (StringValueExp) classNameValue.apply(name);
        } catch (ClassCastException x) {
            // Should not happen - unless someone wrongly implemented
            // StringValueExp.apply().
            final BadStringOperationException y =
                    new BadStringOperationException(x.toString());
            y.initCause(x);
            throw y;
        }

        // Test whether the MBean is an instance of that class.
        try {
            return getMBeanServer().isInstanceOf(name, val.getValue());
        } catch (InstanceNotFoundException infe) {
            return false;
        }
    }

    /**
     * Returns a string representation of this InstanceOfQueryExp.
     * @return a string representation of this InstanceOfQueryExp.
     */
    public String toString() {
       return "InstanceOf " + classNameValue.toString();
   }
}