001/* ClassLoaderRepository.java -- Represents a collection of class loadersx.
002   Copyright (C) 2006 Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038package javax.management.loading;
039
040/**
041 * Implementations of this interface maintain a list of
042 * {@link ClassLoader}s for use by the management servers,
043 * allowing classes to be loaded by the first {@link ClassLoader}
044 * that will do so.  A class loader is added to the list
045 * whenever a {@link ClassLoader} instance is registered with
046 * the management server, and it does not implement the
047 * {@link PrivateClassLoader} interface.  They are removed when
048 * unregistered.  The first class loader in the list is always
049 * the one which was used to load the management server itself.
050 *
051 * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
052 * @since 1.5
053 * @see MBeanServerFactory
054 */
055public interface ClassLoaderRepository
056{
057
058  /**
059   * Attempts to load the given class using class loaders
060   * supplied by the list.  The {@link ClassLoader#loadClass(String)}
061   * method of each class loader is called.  If the method
062   * returns successfully, then the returned {@link Class} instance
063   * is returned.  If a {@link ClassNotFoundException} is thrown,
064   * then the next loader is tried.  Any other exception thrown
065   * by the method is passed back to the caller.  This method
066   * throws a {@link ClassNotFoundException} itself if all the
067   * class loaders listed prove fruitless.
068   *
069   * @param name the name of the class to load.
070   * @return the loaded class.
071   * @throws ClassNotFoundException if all the class loaders fail
072   *                                to load the class.
073   */
074  Class<?> loadClass(String name)
075    throws ClassNotFoundException;
076
077  /**
078   * <p>
079   * Attempts to load the given class using class loaders
080   * supplied by the list, stopping when the specified
081   * loader is reached.  The {@link ClassLoader#loadClass(String)}
082   * method of each class loader is called.  If the method
083   * returns successfully, then the returned {@link Class} instance
084   * is returned.  If a {@link ClassNotFoundException} is thrown,
085   * then the next loader is tried.  Any other exception thrown
086   * by the method is passed back to the caller.  This method
087   * throws a {@link ClassNotFoundException} itself if all the
088   * class loaders listed prove fruitless.
089   * </p>
090   * <p>
091   * This method is usually used by the class loader specified
092   * by the <code>stop</code> argument to load classes using the
093   * loaders that appear before it in the list.  By stopping when
094   * the loader is reached, the deadlock that occurs when the loader
095   * is merely skipped is avoided.
096   * </p>
097   *
098   * @param stop the class loader at which to stop, or <code>null</code>
099   *             to obtain the same behaviour as {@link #loadClass(String)}.
100   * @param name the name of the class to load.
101   * @return the loaded class.
102   * @throws ClassNotFoundException if all the class loaders fail
103   *                                to load the class.
104   */
105  Class<?> loadClassBefore(ClassLoader stop, String name)
106    throws ClassNotFoundException;
107
108  /**
109   * <p>
110   * Attempts to load the given class using class loaders
111   * supplied by the list, excluding the one specified.
112   * The {@link ClassLoader#loadClass(String)}
113   * method of each class loader is called.  If the method
114   * returns successfully, then the returned {@link Class} instance
115   * is returned.  If a {@link ClassNotFoundException} is thrown,
116   * then the next loader is tried.  Any other exception thrown
117   * by the method is passed back to the caller.  This method
118   * throws a {@link ClassNotFoundException} itself if all the
119   * class loaders listed prove fruitless.
120   * </p>
121   * <p>
122   * Note that this method may deadlock if called simultaneously
123   * by two class loaders in the list.
124   * {@link loadClassBefore(ClassLoader, String)} should be used
125   * in preference to this method to avoid this.
126   * </p>
127   *
128   * @param exclude the class loader to exclude, or <code>null</code>
129   *             to obtain the same behaviour as {@link #loadClass(String)}.
130   * @param name the name of the class to load.
131   * @return the loaded class.
132   * @throws ClassNotFoundException if all the class loaders fail
133   *                                to load the class.
134   */
135  Class<?> loadClassWithout(ClassLoader exclude, String name)
136    throws ClassNotFoundException;
137
138}