| J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 1997-2004 Sun Microsystems, Inc. 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. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any 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 | } |