001 /* PermissionCollection.java -- A collection of permission objects
002 Copyright (C) 1998, 2001, 2002, 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
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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.
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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
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031 independent module, the terms and conditions of the license of that
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036 exception statement from your version. */
037
038 package java.security;
039
040 import gnu.java.lang.CPStringBuilder;
041
042 import java.io.Serializable;
043 import java.util.Enumeration;
044
045 /**
046 * This class models a group of Java permissions. It has convenient
047 * methods for determining whether or not a given permission is implied
048 * by any of the permissions in this collection.
049 *
050 * <p>Some care must be taken in storing permissions. First, a collection of
051 * the appropriate type must be created. This is done by calling the
052 * <code>newPermissionCollection</code> method on an object of the
053 * permission class you wish to add to the collection. If this method
054 * returns <code>null</code>, any type of <code>PermissionCollection</code>
055 * can be used to store permissions of that type. However, if a
056 * <code>PermissionCollection</code> collection object is returned, that
057 * type must be used.
058 *
059 * <p>A <code>PermissionCollection</code> returned by the
060 * <code>newPermissionCollection</code> method in a subclass of
061 * <code>Permission</code> is a homogeneous collection. It only will
062 * hold permissions of one specified type - instances of the class that
063 * created it. Not all <code>PermissionCollection</code> subclasses
064 * have to hold permissions of only one type however. For example,
065 * the <code>Permissions</code> class holds permissions of many types.
066 *
067 * <p>Since the <code>newPermissionCollection</code> in <code>Permission</code>
068 * itself returns <code>null</code>, by default a permission can be stored
069 * in any type of collection unless it overrides that method to create its
070 * own collection type.
071 *
072 * @author Aaron M. Renn (arenn@urbanophile.com)
073 * @author Eric Blake (ebb9@email.byu.edu)
074 * @see Permission
075 * @see Permissions
076 * @since 1.1
077 * @status updated to 1.4
078 */
079 public abstract class PermissionCollection implements Serializable
080 {
081 /**
082 * Compatible with JDK 1.1+.
083 */
084 private static final long serialVersionUID = -6727011328946861783L;
085
086 /**
087 * Indicates whether or not this collection is read only.
088 *
089 * @serial if the collection is read-only
090 */
091 private boolean readOnly;
092
093 /**
094 * Create a new collection.
095 */
096 public PermissionCollection()
097 {
098 }
099
100 /**
101 * This method adds a new <code>Permission</code> object to the collection.
102 *
103 * @param perm the <code>Permission</code> to add
104 *
105 * @throws SecurityException if the collection is marked read only
106 * @throws IllegalArgumentException if perm is of the wrong type
107 */
108 public abstract void add(Permission perm);
109
110 /**
111 * This method tests whether the specified <code>Permission</code> object is
112 * implied by this collection of <code>Permission</code> objects.
113 *
114 * @param perm the <code>Permission</code> object to test
115 * @return true if the collection implies perm
116 */
117 public abstract boolean implies(Permission perm);
118
119 /**
120 * This method returns an <code>Enumeration</code> of all the objects in
121 * this collection.
122 *
123 * @return an <code>Enumeration</code> of this collection's objects
124 */
125 public abstract Enumeration<Permission> elements();
126
127 /**
128 * This method sets this <code>PermissionCollection</code> object to be
129 * read only. No further permissions can be added to it after calling this
130 * method.
131 */
132 public void setReadOnly()
133 {
134 readOnly = true;
135 }
136
137 /**
138 * This method tests whether or not this <code>PermissionCollection</code>
139 * object is read only.
140 *
141 * @return true if this collection is read only
142 */
143 public boolean isReadOnly()
144 {
145 return readOnly;
146 }
147
148 /**
149 * This method returns a <code>String</code> representation of this
150 * collection. It is formed by:
151 * <pre>
152 * super.toString()" (\n"
153 * // enumerate all permissions, one per line
154 * ")\n"
155 * </pre>
156 *
157 * @return a <code>String</code> representing this object
158 */
159 public String toString()
160 {
161 CPStringBuilder sb = new CPStringBuilder(super.toString());
162
163 sb.append(" (\n");
164 Enumeration<Permission> e = elements();
165 while (e.hasMoreElements())
166 sb.append(' ').append(e.nextElement()).append('\n');
167 return sb.append(")\n").toString();
168 }
169 } // class PermissionCollection