01: /*
02: * @(#)GuardedObject.java 1.17 06/10/10
03: *
04: * Copyright 1990-2006 Sun Microsystems, Inc. All Rights Reserved.
05: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
06: *
07: * This program is free software; you can redistribute it and/or
08: * modify it under the terms of the GNU General Public License version
09: * 2 only, as published by the Free Software Foundation.
10: *
11: * This program 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 version 2 for more details (a copy is
15: * included at /legal/license.txt).
16: *
17: * You should have received a copy of the GNU General Public License
18: * version 2 along with this work; if not, write to the Free Software
19: * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
20: * 02110-1301 USA
21: *
22: * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
23: * Clara, CA 95054 or visit www.sun.com if you need additional
24: * information or have any questions.
25: *
26: */
27:
28: package java.security;
29:
30: /**
31: * A GuardedObject is an object that is used to protect access to
32: * another object.
33: *
34: * <p>A GuardedObject encapsulates a target object and a Guard object,
35: * such that access to the target object is possible
36: * only if the Guard object allows it.
37: * Once an object is encapsulated by a GuardedObject,
38: * access to that object is controlled by the <code>getObject</code>
39: * method, which invokes the
40: * <code>checkGuard</code> method on the Guard object that is
41: * guarding access. If access is not allowed,
42: * an exception is thrown.
43: *
44: * @see Guard
45: * @see Permission
46: *
47: * @version 1.11 00/02/02
48: * @author Roland Schemers
49: * @author Li Gong
50: */
51:
52: public class GuardedObject implements java.io.Serializable {
53:
54: private Object object; // the object we are guarding
55: private Guard guard; // the guard
56:
57: /**
58: * Constructs a GuardedObject using the specified object and guard.
59: * If the Guard object is null, then no restrictions will
60: * be placed on who can access the object.
61: *
62: * @param object the object to be guarded.
63: *
64: * @param guard the Guard object that guards access to the object.
65: */
66:
67: public GuardedObject(Object object, Guard guard) {
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() throws SecurityException {
82: if (guard != null)
83: guard.checkGuard(object);
84:
85: return object;
86: }
87:
88: /**
89: * Writes this object out to a stream (i.e., serializes it).
90: * We check the guard if there is one.
91: */
92: private synchronized void writeObject(java.io.ObjectOutputStream oos)
93: throws java.io.IOException {
94: if (guard != null)
95: guard.checkGuard(object);
96:
97: oos.defaultWriteObject();
98: }
99: }
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