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