J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 1997-2006 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 | import java.util.*; |
| 29 | |
| 30 | /** |
| 31 | * Abstract class representing a collection of Permission objects. |
| 32 | * |
| 33 | * <p>With a PermissionCollection, you can: |
| 34 | * <UL> |
| 35 | * <LI> add a permission to the collection using the <code>add</code> method. |
| 36 | * <LI> check to see if a particular permission is implied in the |
| 37 | * collection, using the <code>implies</code> method. |
| 38 | * <LI> enumerate all the permissions, using the <code>elements</code> method. |
| 39 | * </UL> |
| 40 | * <P> |
| 41 | * |
| 42 | * <p>When it is desirable to group together a number of Permission objects |
| 43 | * of the same type, the <code>newPermissionCollection</code> method on that |
| 44 | * particular type of Permission object should first be called. The default |
| 45 | * behavior (from the Permission class) is to simply return null. |
| 46 | * Subclasses of class Permission override the method if they need to store |
| 47 | * their permissions in a particular PermissionCollection object in order |
| 48 | * to provide the correct semantics when the |
| 49 | * <code>PermissionCollection.implies</code> method is called. |
| 50 | * If a non-null value is returned, that PermissionCollection must be used. |
| 51 | * If null is returned, then the caller of <code>newPermissionCollection</code> |
| 52 | * is free to store permissions of the |
| 53 | * given type in any PermissionCollection they choose |
| 54 | * (one that uses a Hashtable, one that uses a Vector, etc). |
| 55 | * |
| 56 | * <p>The PermissionCollection returned by the |
| 57 | * <code>Permission.newPermissionCollection</code> |
| 58 | * method is a homogeneous collection, which stores only Permission objects |
| 59 | * for a given Permission type. A PermissionCollection may also be |
| 60 | * heterogeneous. For example, Permissions is a PermissionCollection |
| 61 | * subclass that represents a collection of PermissionCollections. |
| 62 | * That is, its members are each a homogeneous PermissionCollection. |
| 63 | * For example, a Permissions object might have a FilePermissionCollection |
| 64 | * for all the FilePermission objects, a SocketPermissionCollection for all the |
| 65 | * SocketPermission objects, and so on. Its <code>add</code> method adds a |
| 66 | * permission to the appropriate collection. |
| 67 | * |
| 68 | * <p>Whenever a permission is added to a heterogeneous PermissionCollection |
| 69 | * such as Permissions, and the PermissionCollection doesn't yet contain a |
| 70 | * PermissionCollection of the specified permission's type, the |
| 71 | * PermissionCollection should call |
| 72 | * the <code>newPermissionCollection</code> method on the permission's class |
| 73 | * to see if it requires a special PermissionCollection. If |
| 74 | * <code>newPermissionCollection</code> |
| 75 | * returns null, the PermissionCollection |
| 76 | * is free to store the permission in any type of PermissionCollection it |
| 77 | * desires (one using a Hashtable, one using a Vector, etc.). For example, |
| 78 | * the Permissions object uses a default PermissionCollection implementation |
| 79 | * that stores the permission objects in a Hashtable. |
| 80 | * |
| 81 | * <p> Subclass implementations of PermissionCollection should assume |
| 82 | * that they may be called simultaneously from multiple threads, |
| 83 | * and therefore should be synchronized properly. Furthermore, |
| 84 | * Enumerations returned via the <code>elements</code> method are |
| 85 | * not <em>fail-fast</em>. Modifications to a collection should not be |
| 86 | * performed while enumerating over that collection. |
| 87 | * |
| 88 | * @see Permission |
| 89 | * @see Permissions |
| 90 | * |
| 91 | * |
| 92 | * @author Roland Schemers |
| 93 | */ |
| 94 | |
| 95 | public abstract class PermissionCollection implements java.io.Serializable { |
| 96 | |
| 97 | private static final long serialVersionUID = -6727011328946861783L; |
| 98 | |
| 99 | // when set, add will throw an exception. |
| 100 | private volatile boolean readOnly; |
| 101 | |
| 102 | /** |
| 103 | * Adds a permission object to the current collection of permission objects. |
| 104 | * |
| 105 | * @param permission the Permission object to add. |
| 106 | * |
| 107 | * @exception SecurityException - if this PermissionCollection object |
| 108 | * has been marked readonly |
| 109 | * @exception IllegalArgumentException - if this PermissionCollection |
| 110 | * object is a homogeneous collection and the permission |
| 111 | * is not of the correct type. |
| 112 | */ |
| 113 | public abstract void add(Permission permission); |
| 114 | |
| 115 | /** |
| 116 | * Checks to see if the specified permission is implied by |
| 117 | * the collection of Permission objects held in this PermissionCollection. |
| 118 | * |
| 119 | * @param permission the Permission object to compare. |
| 120 | * |
| 121 | * @return true if "permission" is implied by the permissions in |
| 122 | * the collection, false if not. |
| 123 | */ |
| 124 | public abstract boolean implies(Permission permission); |
| 125 | |
| 126 | /** |
| 127 | * Returns an enumeration of all the Permission objects in the collection. |
| 128 | * |
| 129 | * @return an enumeration of all the Permissions. |
| 130 | */ |
| 131 | public abstract Enumeration<Permission> elements(); |
| 132 | |
| 133 | /** |
| 134 | * Marks this PermissionCollection object as "readonly". After |
| 135 | * a PermissionCollection object |
| 136 | * is marked as readonly, no new Permission objects can be added to it |
| 137 | * using <code>add</code>. |
| 138 | */ |
| 139 | public void setReadOnly() { |
| 140 | readOnly = true; |
| 141 | } |
| 142 | |
| 143 | /** |
| 144 | * Returns true if this PermissionCollection object is marked as readonly. |
| 145 | * If it is readonly, no new Permission objects can be added to it |
| 146 | * using <code>add</code>. |
| 147 | * |
| 148 | * <p>By default, the object is <i>not</i> readonly. It can be set to |
| 149 | * readonly by a call to <code>setReadOnly</code>. |
| 150 | * |
| 151 | * @return true if this PermissionCollection object is marked as readonly, |
| 152 | * false otherwise. |
| 153 | */ |
| 154 | public boolean isReadOnly() { |
| 155 | return readOnly; |
| 156 | } |
| 157 | |
| 158 | /** |
| 159 | * Returns a string describing this PermissionCollection object, |
| 160 | * providing information about all the permissions it contains. |
| 161 | * The format is: |
| 162 | * <pre> |
| 163 | * super.toString() ( |
| 164 | * // enumerate all the Permission |
| 165 | * // objects and call toString() on them, |
| 166 | * // one per line.. |
| 167 | * )</pre> |
| 168 | * |
| 169 | * <code>super.toString</code> is a call to the <code>toString</code> |
| 170 | * method of this |
| 171 | * object's superclass, which is Object. The result is |
| 172 | * this PermissionCollection's type name followed by this object's |
| 173 | * hashcode, thus enabling clients to differentiate different |
| 174 | * PermissionCollections object, even if they contain the same permissions. |
| 175 | * |
| 176 | * @return information about this PermissionCollection object, |
| 177 | * as described above. |
| 178 | * |
| 179 | */ |
| 180 | public String toString() { |
| 181 | Enumeration<Permission> enum_ = elements(); |
| 182 | StringBuilder sb = new StringBuilder(); |
| 183 | sb.append(super.toString()+" (\n"); |
| 184 | while (enum_.hasMoreElements()) { |
| 185 | try { |
| 186 | sb.append(" "); |
| 187 | sb.append(enum_.nextElement().toString()); |
| 188 | sb.append("\n"); |
| 189 | } catch (NoSuchElementException e){ |
| 190 | // ignore |
| 191 | } |
| 192 | } |
| 193 | sb.append(")\n"); |
| 194 | return sb.toString(); |
| 195 | } |
| 196 | } |