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      1 /*
      2  * Copyright (c) 1997, 2013, 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}
     37  * method, which invokes the
     38  * {@code checkGuard} 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 }
    103