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8  * particular file as subject to the "Classpath" exception as provided
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13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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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 
GuardedObject(Object object, Guard guard)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      */
getObject()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      */
writeObject(java.io.ObjectOutputStream oos)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