Source Code Cross Referenced for PermissionCollection.java in  » 6.0-JDK-Core » security » java » security » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » 6.0 JDK Core » security » java.security 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001        /*
002         * Copyright 1997-2006 Sun Microsystems, Inc.  All Rights Reserved.
003         * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004         *
005         * This code is free software; you can redistribute it and/or modify it
006         * under the terms of the GNU General Public License version 2 only, as
007         * published by the Free Software Foundation.  Sun designates this
008         * particular file as subject to the "Classpath" exception as provided
009         * by Sun in the LICENSE file that accompanied this code.
010         *
011         * This code is distributed in the hope that it will be useful, but WITHOUT
012         * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013         * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
014         * version 2 for more details (a copy is included in the LICENSE file that
015         * accompanied this code).
016         *
017         * You should have received a copy of the GNU General Public License version
018         * 2 along with this work; if not, write to the Free Software Foundation,
019         * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020         *
021         * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022         * CA 95054 USA or visit www.sun.com if you need additional information or
023         * have any questions.
024         */
025
026        package java.security;
027
028        import java.util.*;
029
030        /**
031         * Abstract class representing a collection of Permission objects.
032         *
033         * <p>With a PermissionCollection, you can:
034         * <UL>
035         * <LI> add a permission to the collection using the <code>add</code> method.
036         * <LI> check to see if a particular permission is implied in the
037         *      collection, using the <code>implies</code> method.
038         * <LI> enumerate all the permissions, using the <code>elements</code> method.
039         * </UL>
040         * <P>
041         *
042         * <p>When it is desirable to group together a number of Permission objects
043         * of the same type, the <code>newPermissionCollection</code> method on that
044         * particular type of Permission object should first be called. The default
045         * behavior (from the Permission class) is to simply return null.
046         * Subclasses of class Permission override the method if they need to store
047         * their permissions in a particular PermissionCollection object in order
048         * to provide the correct semantics when the
049         * <code>PermissionCollection.implies</code> method is called.
050         * If a non-null value is returned, that PermissionCollection must be used.
051         * If null is returned, then the caller of <code>newPermissionCollection</code>
052         * is free to store permissions of the
053         * given type in any PermissionCollection they choose
054         * (one that uses a Hashtable, one that uses a Vector, etc).
055         *
056         * <p>The PermissionCollection returned by the
057         * <code>Permission.newPermissionCollection</code>
058         * method is a homogeneous collection, which stores only Permission objects
059         * for a given Permission type.  A PermissionCollection may also be
060         * heterogeneous.  For example, Permissions is a PermissionCollection
061         * subclass that represents a collection of PermissionCollections.
062         * That is, its members are each a homogeneous PermissionCollection.
063         * For example, a Permissions object might have a FilePermissionCollection
064         * for all the FilePermission objects, a SocketPermissionCollection for all the
065         * SocketPermission objects, and so on. Its <code>add</code> method adds a
066         * permission to the appropriate collection.
067         *
068         * <p>Whenever a permission is added to a heterogeneous PermissionCollection
069         * such as Permissions, and the PermissionCollection doesn't yet contain a
070         * PermissionCollection of the specified permission's type, the
071         * PermissionCollection should call
072         * the <code>newPermissionCollection</code> method on the permission's class
073         * to see if it requires a special PermissionCollection. If
074         * <code>newPermissionCollection</code>
075         * returns null, the PermissionCollection
076         * is free to store the permission in any type of PermissionCollection it
077         * desires (one using a Hashtable, one using a Vector, etc.). For example,
078         * the Permissions object uses a default PermissionCollection implementation
079         * that stores the permission objects in a Hashtable.
080         *
081         * <p> Subclass implementations of PermissionCollection should assume
082         * that they may be called simultaneously from multiple threads,
083         * and therefore should be synchronized properly.  Furthermore,
084         * Enumerations returned via the <code>elements</code> method are
085         * not <em>fail-fast</em>.  Modifications to a collection should not be
086         * performed while enumerating over that collection.
087         *
088         * @see Permission
089         * @see Permissions
090         *
091         * @version 1.44 07/07/30
092         *
093         * @author Roland Schemers
094         */
095
096        public abstract class PermissionCollection implements 
097                java.io.Serializable {
098
099            private static final long serialVersionUID = -6727011328946861783L;
100
101            // when set, add will throw an exception.
102            private volatile boolean readOnly;
103
104            /**
105             * Adds a permission object to the current collection of permission objects.
106             *
107             * @param permission the Permission object to add.
108             *
109             * @exception SecurityException -  if this PermissionCollection object
110             *                                 has been marked readonly
111             * @exception IllegalArgumentException - if this PermissionCollection
112             *                object is a homogeneous collection and the permission
113             *                is not of the correct type.
114             */
115            public abstract void add(Permission permission);
116
117            /**
118             * Checks to see if the specified permission is implied by
119             * the collection of Permission objects held in this PermissionCollection.
120             *
121             * @param permission the Permission object to compare.
122             *
123             * @return true if "permission" is implied by the  permissions in
124             * the collection, false if not.
125             */
126            public abstract boolean implies(Permission permission);
127
128            /**
129             * Returns an enumeration of all the Permission objects in the collection.
130             *
131             * @return an enumeration of all the Permissions.
132             */
133            public abstract Enumeration<Permission> elements();
134
135            /**
136             * Marks this PermissionCollection object as "readonly". After
137             * a PermissionCollection object
138             * is marked as readonly, no new Permission objects can be added to it
139             * using <code>add</code>.
140             */
141            public void setReadOnly() {
142                readOnly = true;
143            }
144
145            /**
146             * Returns true if this PermissionCollection object is marked as readonly.
147             * If it is readonly, no new Permission objects can be added to it
148             * using <code>add</code>.
149             *
150             * <p>By default, the object is <i>not</i> readonly. It can be set to
151             * readonly by a call to <code>setReadOnly</code>.
152             *
153             * @return true if this PermissionCollection object is marked as readonly,
154             * false otherwise.
155             */
156            public boolean isReadOnly() {
157                return readOnly;
158            }
159
160            /**
161             * Returns a string describing this PermissionCollection object,
162             * providing information about all the permissions it contains.
163             * The format is:
164             * <pre>
165             * super.toString() (
166             *   // enumerate all the Permission
167             *   // objects and call toString() on them,
168             *   // one per line..
169             * )</pre>
170             *
171             * <code>super.toString</code> is a call to the <code>toString</code>
172             * method of this
173             * object's superclass, which is Object. The result is
174             * this PermissionCollection's type name followed by this object's
175             * hashcode, thus enabling clients to differentiate different
176             * PermissionCollections object, even if they contain the same permissions.
177             *
178             * @return information about this PermissionCollection object,
179             *         as described above.
180             *
181             */
182            public String toString() {
183                Enumeration<Permission> enum_ = elements();
184                StringBuilder sb = new StringBuilder();
185                sb.append(super .toString() + " (\n");
186                while (enum_.hasMoreElements()) {
187                    try {
188                        sb.append(" ");
189                        sb.append(enum_.nextElement().toString());
190                        sb.append("\n");
191                    } catch (NoSuchElementException e) {
192                        // ignore
193                    }
194                }
195                sb.append(")\n");
196                return sb.toString();
197            }
198        }
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