001/* GuardedObject.java -- An object protected by a Guard
002   Copyright (C) 1998, 2002, 2004, 2005  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
038
039package java.security;
040
041import java.io.IOException;
042import java.io.ObjectOutputStream;
043import java.io.Serializable;
044
045/**
046 * This class is an object that is guarded by a <code>Guard</code> object.
047 * The object that is being guarded is retrieved by a call to the only
048 * method in this class - <code>getObject</code>.  That method returns the
049 * guarded <code>Object</code> after first checking with the
050 * <code>Guard</code>.  If the <code>Guard</code> disallows access, an
051 * exception will be thrown.
052 *
053 * @author Aaron M. Renn (arenn@urbanophile.com)
054 * @since 1.1
055 * @status updated to 1.4
056 */
057public class GuardedObject implements Serializable
058{
059  /**
060   * Compatible with JDK 1.1+.
061   */
062  private static final long serialVersionUID = -5240450096227834308L;
063
064  /**
065   * This is the Guard that is protecting the object.
066   *
067   * @serial the guard
068   */
069  private final Guard guard;
070
071  /**
072   * This is the object that is being guarded.
073   *
074   * @serial the protected object
075   */
076  private final Object object;
077
078  /**
079   * This method initializes a new instance of <code>GuardedObject</code>
080   * that protects the specified <code>Object</code> using the specified
081   * <code>Guard</code>. A null guard means there are no restrictions on
082   * accessing the object.
083   *
084   * @param object the <code>Object</code> to guard
085   * @param guard the <code>Guard</code> that is protecting the object
086   */
087  public GuardedObject(Object object, Guard guard)
088  {
089    this.object = object;
090    this.guard = guard;
091  }
092
093  /**
094   * This method first call the <code>checkGuard</code> method on the
095   * <code>Guard</code> object protecting the guarded object.  If the
096   * <code>Guard</code> disallows access, an exception is thrown, otherwise
097   * the <code>Object</code> is returned.
098   *
099   * @return The object being guarded
100   * @throws SecurityException if access is denied
101   */
102  public Object getObject()
103  {
104    if (guard != null)
105      guard.checkGuard(object);
106    return object;
107  }
108
109  /**
110   * Ensures that serialization is legal, by checking the guard.
111   *
112   * @param s the stream to write to
113   * @throws IOException if the underlying stream fails
114   */
115  private void writeObject(ObjectOutputStream s) throws IOException
116  {
117    if (guard != null)
118      guard.checkGuard(object);
119    s.defaultWriteObject();
120  }
121} // class GuardedObject