Source for java.security.GuardedObject

   1: /* GuardedObject.java -- An object protected by a Guard
   2:    Copyright (C) 1998, 2002, 2004, 2005  Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: 
  39: package java.security;
  40: 
  41: import java.io.IOException;
  42: import java.io.ObjectOutputStream;
  43: import java.io.Serializable;
  44: 
  45: /**
  46:  * This class is an object that is guarded by a <code>Guard</code> object.
  47:  * The object that is being guarded is retrieved by a call to the only
  48:  * method in this class - <code>getObject</code>.  That method returns the
  49:  * guarded <code>Object</code> after first checking with the
  50:  * <code>Guard</code>.  If the <code>Guard</code> disallows access, an
  51:  * exception will be thrown.
  52:  *
  53:  * @author Aaron M. Renn (arenn@urbanophile.com)
  54:  * @since 1.1
  55:  * @status updated to 1.4
  56:  */
  57: public class GuardedObject implements Serializable
  58: {
  59:   /**
  60:    * Compatible with JDK 1.1+.
  61:    */
  62:   private static final long serialVersionUID = -5240450096227834308L;
  63: 
  64:   /**
  65:    * This is the Guard that is protecting the object.
  66:    *
  67:    * @serial the guard
  68:    */
  69:   private final Guard guard;
  70: 
  71:   /**
  72:    * This is the object that is being guarded.
  73:    *
  74:    * @serial the protected object
  75:    */
  76:   private final Object object;
  77: 
  78:   /**
  79:    * This method initializes a new instance of <code>GuardedObject</code>
  80:    * that protects the specified <code>Object</code> using the specified
  81:    * <code>Guard</code>. A null guard means there are no restrictions on
  82:    * accessing the object.
  83:    *
  84:    * @param object the <code>Object</code> to guard
  85:    * @param guard the <code>Guard</code> that is protecting the object
  86:    */
  87:   public GuardedObject(Object object, Guard guard)
  88:   {
  89:     this.object = object;
  90:     this.guard = guard;
  91:   }
  92: 
  93:   /**
  94:    * This method first call the <code>checkGuard</code> method on the
  95:    * <code>Guard</code> object protecting the guarded object.  If the
  96:    * <code>Guard</code> disallows access, an exception is thrown, otherwise
  97:    * the <code>Object</code> is returned.
  98:    *
  99:    * @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