libjava/classpath/javax/management/loading/ClassLoaderRepository.java

/* ClassLoaderRepository.java -- Represents a collection of class loadersx.
   Copyright (C) 2006 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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any later version.

GNU Classpath is distributed in the hope that it will be useful, but
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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02110-1301 USA.

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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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this exception to your version of the library, but you are not
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package javax.management.loading;

/**
 * Implementations of this interface maintain a list of
 * {@link ClassLoader}s for use by the management servers,
 * allowing classes to be loaded by the first {@link ClassLoader}
 * that will do so.  A class loader is added to the list
 * whenever a {@link ClassLoader} instance is registered with
 * the management server, and it does not implement the
 * {@link PrivateClassLoader} interface.  They are removed when
 * unregistered.  The first class loader in the list is always
 * the one which was used to load the management server itself.
 *
 * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
 * @since 1.5
 * @see MBeanServerFactory
 */
public interface ClassLoaderRepository
{

  /**
   * Attempts to load the given class using class loaders
   * supplied by the list.  The {@link ClassLoader#loadClass(String)}
   * method of each class loader is called.  If the method
   * returns successfully, then the returned {@link Class} instance
   * is returned.  If a {@link ClassNotFoundException} is thrown,
   * then the next loader is tried.  Any other exception thrown
   * by the method is passed back to the caller.  This method
   * throws a {@link ClassNotFoundException} itself if all the
   * class loaders listed prove fruitless.
   *
   * @param name the name of the class to load.
   * @return the loaded class.
   * @throws ClassNotFoundException if all the class loaders fail
   *                                to load the class.
   */
  Class<?> loadClass(String name)
    throws ClassNotFoundException;

  /**
   * <p>
   * Attempts to load the given class using class loaders
   * supplied by the list, stopping when the specified
   * loader is reached.  The {@link ClassLoader#loadClass(String)}
   * method of each class loader is called.  If the method
   * returns successfully, then the returned {@link Class} instance
   * is returned.  If a {@link ClassNotFoundException} is thrown,
   * then the next loader is tried.  Any other exception thrown
   * by the method is passed back to the caller.  This method
   * throws a {@link ClassNotFoundException} itself if all the
   * class loaders listed prove fruitless.
   * </p>
   * <p>
   * This method is usually used by the class loader specified
   * by the <code>stop</code> argument to load classes using the
   * loaders that appear before it in the list.  By stopping when
   * the loader is reached, the deadlock that occurs when the loader
   * is merely skipped is avoided.
   * </p>
   *
   * @param stop the class loader at which to stop, or <code>null</code>
   *             to obtain the same behaviour as {@link #loadClass(String)}.
   * @param name the name of the class to load.
   * @return the loaded class.
   * @throws ClassNotFoundException if all the class loaders fail
   *                                to load the class.
   */
  Class<?> loadClassBefore(ClassLoader stop, String name)
    throws ClassNotFoundException;

  /**
   * <p>
   * Attempts to load the given class using class loaders
   * supplied by the list, excluding the one specified.
   * The {@link ClassLoader#loadClass(String)}
   * method of each class loader is called.  If the method
   * returns successfully, then the returned {@link Class} instance
   * is returned.  If a {@link ClassNotFoundException} is thrown,
   * then the next loader is tried.  Any other exception thrown
   * by the method is passed back to the caller.  This method
   * throws a {@link ClassNotFoundException} itself if all the
   * class loaders listed prove fruitless.
   * </p>
   * <p>
   * Note that this method may deadlock if called simultaneously
   * by two class loaders in the list.
   * {@link loadClassBefore(ClassLoader, String)} should be used
   * in preference to this method to avoid this.
   * </p>
   *
   * @param exclude the class loader to exclude, or <code>null</code>
   *             to obtain the same behaviour as {@link #loadClass(String)}.
   * @param name the name of the class to load.
   * @return the loaded class.
   * @throws ClassNotFoundException if all the class loaders fail
   *                                to load the class.
   */
  Class<?> loadClassWithout(ClassLoader exclude, String name)
    throws ClassNotFoundException;

}