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. 010 011 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. 015 016 You should have received a copy of the GNU General Public License 017 along with GNU Classpath; see the file COPYING. If not, write to the 018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 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 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