001 /* Permissions.java -- a collection of permission collections
002 Copyright (C) 1998, 2001, 2002, 2004, 2005 Free Software Foundation, Inc.
003
004 This file is part of GNU Classpath.
005
006 GNU Classpath is free software; you can redistribute it and/or modify
007 it under the terms of the GNU General Public License as published by
008 the Free Software Foundation; either version 2, or (at your option)
009 any later version.
010
011 GNU Classpath is distributed in the hope that it will be useful, but
012 WITHOUT ANY WARRANTY; without even the implied warranty of
013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014 General Public License for more details.
015
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017 along with GNU Classpath; see the file COPYING. If not, write to the
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019 02110-1301 USA.
020
021 Linking this library statically or dynamically with other modules is
022 making a combined work based on this library. Thus, the terms and
023 conditions of the GNU General Public License cover the whole
024 combination.
025
026 As a special exception, the copyright holders of this library give you
027 permission to link this library with independent modules to produce an
028 executable, regardless of the license terms of these independent
029 modules, and to copy and distribute the resulting executable under
030 terms of your choice, provided that you also meet, for each linked
031 independent module, the terms and conditions of the license of that
032 module. An independent module is a module which is not derived from
033 or based on this library. If you modify this library, you may extend
034 this exception to your version of the library, but you are not
035 obligated to do so. If you do not wish to do so, delete this
036 exception statement from your version. */
037
038
039 package java.security;
040
041 import java.io.Serializable;
042 import java.util.Enumeration;
043 import java.util.Hashtable;
044 import java.util.NoSuchElementException;
045
046 /**
047 * This class is a heterogeneous collection of permissions. It is
048 * organized as a collection of <code>PermissionCollection</code>'s stored
049 * in a hashtable. Each individual <code>PermissionCollection</code>
050 * contains permissions of a single type. If a specific type of
051 * <code>Permission</code> does not provide a collection type to use
052 * via its <code>newPermissionCollection</code> method, then a default
053 * collection type which stores its permissions in a hash table will be
054 * used.
055 *
056 * @author Aaron M. Renn (arenn@urbanophile.com)
057 * @author Eric Blake (ebb9@email.byu.edu)
058 * @since 1.1
059 */
060 public final class Permissions extends PermissionCollection
061 implements Serializable
062 {
063 /**
064 * Compatible with JDK 1.1+.
065 */
066 private static final long serialVersionUID = 4858622370623524688L;
067
068 /**
069 * Holds instances of <code>AllPermission</code>.
070 *
071 * @serial the permission collection for AllPermission
072 */
073 private PermissionCollection allPermission;
074
075 // Package-private to avoid a trampoline.
076 /**
077 * This is the <code>Hashtable</code> that contains our collections.
078 *
079 * @serial maps Class to PermissionCollection
080 */
081 final Hashtable perms = new Hashtable();
082
083 /**
084 * This method initializes a new instance of <code>Permissions</code>.
085 */
086 public Permissions()
087 {
088 }
089
090 /**
091 * This method adds a new <code>Permission</code> to this collection. It
092 * will be stored in a <code>PermissionCollection</code> of the appropriate
093 * type, as determined by calling <code>newPermissionCollection</code> on
094 * the specified permission (if an appropriate collection does not already
095 * exist). If this object does not specify a particular type of collection,
096 * a default collection, which stores in permissions in a hash table, will
097 * be used.
098 *
099 * @param perm the <code>Permission</code> to add
100 * @throws SecurityException if this collection is marked as read only
101 */
102 public void add(Permission perm)
103 {
104 if (isReadOnly())
105 throw new SecurityException("PermissionCollection is read only");
106 if (perm instanceof AllPermission)
107 {
108 if (allPermission == null)
109 {
110 allPermission = perm.newPermissionCollection();
111 allPermission.add(perm);
112 perms.put(perm.getClass(), allPermission);
113 }
114 }
115 else
116 {
117 PermissionCollection pc
118 = (PermissionCollection) perms.get(perm.getClass());
119 if (pc == null)
120 {
121 pc = perm.newPermissionCollection();
122 if (pc == null)
123 pc = new PermissionsHash();
124 perms.put(perm.getClass(), pc);
125 }
126 pc.add(perm);
127 }
128 }
129
130 /**
131 * This method tests whether or not the specified <code>Permission</code>
132 * is implied by this <code>PermissionCollection</code>.
133 *
134 * @param perm the <code>Permission</code> to test
135 * @return true if the specified permission is implied by this
136 */
137 public boolean implies(Permission perm)
138 {
139 if (allPermission != null)
140 return true;
141 PermissionCollection pc
142 = (PermissionCollection) perms.get(perm.getClass());
143 return pc == null ? false : pc.implies(perm);
144 }
145
146 /**
147 * This method returns an <code>Enumeration</code> which contains a
148 * list of all <code>Permission</code> objects contained in this
149 * collection.
150 *
151 * @return an <code>Enumeration</code> of this collection's elements
152 */
153 public Enumeration<Permission> elements()
154 {
155 return new Enumeration()
156 {
157 Enumeration main_enum = perms.elements();
158 Enumeration sub_enum;
159
160 public boolean hasMoreElements()
161 {
162 if (sub_enum == null)
163 {
164 if (main_enum == null)
165 return false;
166 if (! main_enum.hasMoreElements())
167 {
168 main_enum = null;
169 return false;
170 }
171 PermissionCollection pc =
172 (PermissionCollection) main_enum.nextElement();
173 sub_enum = pc.elements();
174 }
175 if (! sub_enum.hasMoreElements())
176 {
177 sub_enum = null;
178 return hasMoreElements();
179 }
180 return true;
181 }
182
183 public Object nextElement()
184 {
185 if (! hasMoreElements())
186 throw new NoSuchElementException();
187 return sub_enum.nextElement();
188 }
189 };
190 }
191
192 /**
193 * Implements the permission collection for all permissions without one of
194 * their own, and obeys serialization of JDK.
195 *
196 * @author Eric Blake (ebb9@email.byu.edu)
197 */
198 private static final class PermissionsHash extends PermissionCollection
199 {
200 /**
201 * Compatible with JDK 1.1+.
202 */
203 private static final long serialVersionUID = -8491988220802933440L;
204
205 /**
206 * Hashtable where we store permissions.
207 *
208 * @serial the stored permissions, both as key and value
209 */
210 private final Hashtable perms = new Hashtable();
211
212 /**
213 * Add a permission. We don't need to check for read-only, as this
214 * collection is never exposed outside of Permissions, which has already
215 * done that check.
216 *
217 * @param perm the permission to add
218 */
219 public void add(Permission perm)
220 {
221 perms.put(perm, perm);
222 }
223
224 /**
225 * Returns true if perm is in the collection.
226 *
227 * @param perm the permission to check
228 * @return true if it is implied
229 */
230 // FIXME: Should this method be synchronized?
231 public boolean implies(Permission perm)
232 {
233 Enumeration elements = elements();
234
235 while (elements.hasMoreElements())
236 {
237 Permission p = (Permission)elements.nextElement();
238 if (p.implies(perm))
239 return true;
240 }
241 return false;
242 }
243
244 /**
245 * Return the elements.
246 *
247 * @return the elements
248 */
249 public Enumeration elements()
250 {
251 return perms.elements();
252 }
253 } // class PermissionsHash
254 } // class Permissions