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    1   /*
    2    * Copyright (c) 1997, 2004, Oracle and/or its affiliates. All rights reserved.
    3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
    4    *
    5    * This code is free software; you can redistribute it and/or modify it
    6    * under the terms of the GNU General Public License version 2 only, as
    7    * published by the Free Software Foundation.  Oracle designates this
    8    * particular file as subject to the "Classpath" exception as provided
    9    * by Oracle in the LICENSE file that accompanied this code.
   10    *
   11    * This code is distributed in the hope that it will be useful, but WITHOUT
   12    * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   13    * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   14    * version 2 for more details (a copy is included in the LICENSE file that
   15    * accompanied this code).
   16    *
   17    * You should have received a copy of the GNU General Public License version
   18    * 2 along with this work; if not, write to the Free Software Foundation,
   19    * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   20    *
   21    * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   22    * or visit www.oracle.com if you need additional information or have any
   23    * questions.
   24    */
   25   
   26   package java.security;
   27   
   28   /**
   29    * A GuardedObject is an object that is used to protect access to
   30    * another object.
   31    *
   32    * <p>A GuardedObject encapsulates a target object and a Guard object,
   33    * such that access to the target object is possible
   34    * only if the Guard object allows it.
   35    * Once an object is encapsulated by a GuardedObject,
   36    * access to that object is controlled by the <code>getObject</code>
   37    * method, which invokes the
   38    * <code>checkGuard</code> method on the Guard object that is
   39    * guarding access. If access is not allowed,
   40    * an exception is thrown.
   41    *
   42    * @see Guard
   43    * @see Permission
   44    *
   45    * @author Roland Schemers
   46    * @author Li Gong
   47    */
   48   
   49   public class GuardedObject implements java.io.Serializable {
   50   
   51       private static final long serialVersionUID = -5240450096227834308L;
   52   
   53       private Object object; // the object we are guarding
   54       private Guard guard;   // the guard
   55   
   56       /**
   57        * Constructs a GuardedObject using the specified object and guard.
   58        * If the Guard object is null, then no restrictions will
   59        * be placed on who can access the object.
   60        *
   61        * @param object the object to be guarded.
   62        *
   63        * @param guard the Guard object that guards access to the object.
   64        */
   65   
   66       public GuardedObject(Object object, Guard guard)
   67       {
   68           this.guard = guard;
   69           this.object = object;
   70       }
   71   
   72       /**
   73        * Retrieves the guarded object, or throws an exception if access
   74        * to the guarded object is denied by the guard.
   75        *
   76        * @return the guarded object.
   77        *
   78        * @exception SecurityException if access to the guarded object is
   79        * denied.
   80        */
   81       public Object getObject()
   82           throws SecurityException
   83       {
   84           if (guard != null)
   85               guard.checkGuard(object);
   86   
   87           return object;
   88       }
   89   
   90       /**
   91        * Writes this object out to a stream (i.e., serializes it).
   92        * We check the guard if there is one.
   93        */
   94       private void writeObject(java.io.ObjectOutputStream oos)
   95           throws java.io.IOException
   96       {
   97           if (guard != null)
   98               guard.checkGuard(object);
   99   
  100           oos.defaultWriteObject();
  101       }
  102   }

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