001/* GuardedObject.java -- An object protected by a Guard 002 Copyright (C) 1998, 2002, 2004, 2005 Free Software Foundation, Inc. 003 004This file is part of GNU Classpath. 005 006GNU Classpath is free software; you can redistribute it and/or modify 007it under the terms of the GNU General Public License as published by 008the Free Software Foundation; either version 2, or (at your option) 009any later version. 010 011GNU Classpath is distributed in the hope that it will be useful, but 012WITHOUT ANY WARRANTY; without even the implied warranty of 013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 014General Public License for more details. 015 016You should have received a copy of the GNU General Public License 017along with GNU Classpath; see the file COPYING. If not, write to the 018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 01902110-1301 USA. 020 021Linking this library statically or dynamically with other modules is 022making a combined work based on this library. Thus, the terms and 023conditions of the GNU General Public License cover the whole 024combination. 025 026As a special exception, the copyright holders of this library give you 027permission to link this library with independent modules to produce an 028executable, regardless of the license terms of these independent 029modules, and to copy and distribute the resulting executable under 030terms of your choice, provided that you also meet, for each linked 031independent module, the terms and conditions of the license of that 032module. An independent module is a module which is not derived from 033or based on this library. If you modify this library, you may extend 034this exception to your version of the library, but you are not 035obligated to do so. If you do not wish to do so, delete this 036exception statement from your version. */ 037 038 039package java.security; 040 041import java.io.IOException; 042import java.io.ObjectOutputStream; 043import java.io.Serializable; 044 045/** 046 * This class is an object that is guarded by a <code>Guard</code> object. 047 * The object that is being guarded is retrieved by a call to the only 048 * method in this class - <code>getObject</code>. That method returns the 049 * guarded <code>Object</code> after first checking with the 050 * <code>Guard</code>. If the <code>Guard</code> disallows access, an 051 * exception will be thrown. 052 * 053 * @author Aaron M. Renn (arenn@urbanophile.com) 054 * @since 1.1 055 * @status updated to 1.4 056 */ 057public class GuardedObject implements Serializable 058{ 059 /** 060 * Compatible with JDK 1.1+. 061 */ 062 private static final long serialVersionUID = -5240450096227834308L; 063 064 /** 065 * This is the Guard that is protecting the object. 066 * 067 * @serial the guard 068 */ 069 private final Guard guard; 070 071 /** 072 * This is the object that is being guarded. 073 * 074 * @serial the protected object 075 */ 076 private final Object object; 077 078 /** 079 * This method initializes a new instance of <code>GuardedObject</code> 080 * that protects the specified <code>Object</code> using the specified 081 * <code>Guard</code>. A null guard means there are no restrictions on 082 * accessing the object. 083 * 084 * @param object the <code>Object</code> to guard 085 * @param guard the <code>Guard</code> that is protecting the object 086 */ 087 public GuardedObject(Object object, Guard guard) 088 { 089 this.object = object; 090 this.guard = guard; 091 } 092 093 /** 094 * This method first call the <code>checkGuard</code> method on the 095 * <code>Guard</code> object protecting the guarded object. If the 096 * <code>Guard</code> disallows access, an exception is thrown, otherwise 097 * the <code>Object</code> is returned. 098 * 099 * @return The object being guarded 100 * @throws SecurityException if access is denied 101 */ 102 public Object getObject() 103 { 104 if (guard != null) 105 guard.checkGuard(object); 106 return object; 107 } 108 109 /** 110 * Ensures that serialization is legal, by checking the guard. 111 * 112 * @param s the stream to write to 113 * @throws IOException if the underlying stream fails 114 */ 115 private void writeObject(ObjectOutputStream s) throws IOException 116 { 117 if (guard != null) 118 guard.checkGuard(object); 119 s.defaultWriteObject(); 120 } 121} // class GuardedObject