001/* QueryEval.java -- An evaluation context for a MBean server query.
002   Copyright (C) 2007 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;
039
040import java.io.Serializable;
041
042/**
043 * Represents the evaluation context of a {@link MBeanServer}
044 * query by retaining the server used on a thread-by-thread
045 * basis.
046 *
047 * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
048 * @since 1.5
049 */
050public class QueryEval
051  implements Serializable
052{
053
054  /**
055   * Compatible with JDK 1.5
056   */
057  private static final long serialVersionUID = 2675899265640874796L;
058
059  /**
060   * Stores the server used, on a 
061   * thread-by-thread basis.
062   */
063  private static InheritableThreadLocal<MBeanServer> server =
064    new InheritableThreadLocal<MBeanServer>();
065
066  /**
067   * Returns the {@link MBeanServer} last supplied to the
068   * {@link #setMBeanServer(MBeanServer)} method.  If this method
069   * has not been called for this thread, then the value will be
070   * inherited from any parent thread on which the method has
071   * been called.  If the method has never been called, then
072   * <code>null</code> is returned.
073   *
074   * @return the server.
075   * @see #setMBeanServer(MBeanServer)
076   */
077  public static MBeanServer getMBeanServer()
078  {
079    return server.get();
080  }
081
082  /**
083   * Sets the {@link MBeanServer} on which the query will be
084   * performed.  This value is inherited automatically by
085   * child threads.  This method is only non-static for historical
086   * reasons; it makes no use of instance-related values. 
087   *
088   * @param svr the server to use.
089   */
090  public void setMBeanServer(MBeanServer svr)
091  {
092    server.set(svr);
093  }
094
095}