Java example source code file (ClassLoaderRepository.java)

This example Java source code file (ClassLoaderRepository.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

class, classloaderrepository, classnotfoundexception, management, string

The ClassLoaderRepository.java Java example source code

/*
 * Copyright (c) 2002, 2007, 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.loading;

import javax.management.MBeanServer; // for Javadoc

/**
 * <p>Instances of this interface are used to keep the list of ClassLoaders
 * registered in an MBean Server.
 * They provide the necessary methods to load classes using the registered
 * ClassLoaders.</p>
 *
 * <p>The first ClassLoader in a ClassLoaderRepository is
 * always the MBean Server's own ClassLoader.</p>
 *
 * <p>When an MBean is registered in an MBean Server, if it is of a
 * subclass of {@link java.lang.ClassLoader} and if it does not
 * implement the interface {@link PrivateClassLoader}, it is added to
 * the end of the MBean Server's <code>ClassLoaderRepository.
 * If it is subsequently unregistered from the MBean Server, it is
 * removed from the <code>ClassLoaderRepository.

 *
 * <p>The order of MBeans in the ClassLoaderRepository is
 * significant.  For any two MBeans <em>X and Y in the
 * <code>ClassLoaderRepository, X must appear before
 * <em>Y if the registration of X was completed before
 * the registration of <em>Y started.  If X and
 * <em>Y were registered concurrently, their order is
 * indeterminate.  The registration of an MBean corresponds to the
 * call to {@link MBeanServer#registerMBean} or one of the {@link
 * MBeanServer}<code>.createMBean methods.

 *
 * @see javax.management.MBeanServerFactory
 *
 * @since 1.5
 */
public interface ClassLoaderRepository {

    /**
     * <p>Load the given class name through the list of class loaders.
     * Each ClassLoader in turn from the ClassLoaderRepository is
     * asked to load the class via its {@link
     * ClassLoader#loadClass(String)} method.  If it successfully
     * returns a {@link Class} object, that is the result of this
     * method.  If it throws a {@link ClassNotFoundException}, the
     * search continues with the next ClassLoader.  If it throws
     * another exception, the exception is propagated from this
     * method.  If the end of the list is reached, a {@link
     * ClassNotFoundException} is thrown.</p>
     *
     * @param className The name of the class to be loaded.
     *
     * @return the loaded class.
     *
     * @exception ClassNotFoundException The specified class could not be
     *            found.
     */
    public Class<?> loadClass(String className)
            throws ClassNotFoundException;

    /**
     * <p>Load the given class name through the list of class loaders,
     * excluding the given one.  Each ClassLoader in turn from the
     * ClassLoaderRepository, except <code>exclude, is asked to
     * load the class via its {@link ClassLoader#loadClass(String)}
     * method.  If it successfully returns a {@link Class} object,
     * that is the result of this method.  If it throws a {@link
     * ClassNotFoundException}, the search continues with the next
     * ClassLoader.  If it throws another exception, the exception is
     * propagated from this method.  If the end of the list is
     * reached, a {@link ClassNotFoundException} is thrown.</p>
     *
     * <p>Be aware that if a ClassLoader in the ClassLoaderRepository
     * calls this method from its {@link ClassLoader#loadClass(String)
     * loadClass} method, it exposes itself to a deadlock if another
     * ClassLoader in the ClassLoaderRepository does the same thing at
     * the same time.  The {@link #loadClassBefore} method is
     * recommended to avoid the risk of deadlock.</p>
     *
     * @param className The name of the class to be loaded.
     * @param exclude The class loader to be excluded.  May be null,
     * in which case this method is equivalent to {@link #loadClass
     * loadClass(className)}.
     *
     * @return the loaded class.
     *
     * @exception ClassNotFoundException The specified class could not
     * be found.
     */
    public Class<?> loadClassWithout(ClassLoader exclude,
                                     String className)
            throws ClassNotFoundException;

    /**
     * <p>Load the given class name through the list of class loaders,
     * stopping at the given one.  Each ClassLoader in turn from the
     * ClassLoaderRepository is asked to load the class via its {@link
     * ClassLoader#loadClass(String)} method.  If it successfully
     * returns a {@link Class} object, that is the result of this
     * method.  If it throws a {@link ClassNotFoundException}, the
     * search continues with the next ClassLoader.  If it throws
     * another exception, the exception is propagated from this
     * method.  If the search reaches <code>stop or the end of
     * the list, a {@link ClassNotFoundException} is thrown.</p>
     *
     * <p>Typically this method is called from the {@link
     * ClassLoader#loadClass(String) loadClass} method of
     * <code>stop, to consult loaders that appear before it
     * in the <code>ClassLoaderRepository.  By stopping the
     * search as soon as <code>stop is reached, a potential
     * deadlock with concurrent class loading is avoided.</p>
     *
     * @param className The name of the class to be loaded.
     * @param stop The class loader at which to stop.  May be null, in
     * which case this method is equivalent to {@link #loadClass(String)
     * loadClass(className)}.
     *
     * @return the loaded class.
     *
     * @exception ClassNotFoundException The specified class could not
     * be found.
     *
     */
    public Class<?> loadClassBefore(ClassLoader stop,
                                    String className)
            throws ClassNotFoundException;

}