Source for java.security.Permissions

   1: /* Permissions.java -- a collection of permission collections
   2:    Copyright (C) 1998, 2001, 2002, 2004, 2005  Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: 
  39: package java.security;
  40: 
  41: import java.io.Serializable;
  42: import java.util.Enumeration;
  43: import java.util.Hashtable;
  44: import java.util.NoSuchElementException;
  45: 
  46: /**
  47:  * This class is a heterogeneous collection of permissions.  It is
  48:  * organized as a collection of <code>PermissionCollection</code>'s stored
  49:  * in a hashtable.  Each individual <code>PermissionCollection</code>
  50:  * contains permissions of a single type.  If a specific type of
  51:  * <code>Permission</code> does not provide a collection type to use
  52:  * via its <code>newPermissionCollection</code> method, then a default
  53:  * collection type which stores its permissions in a hash table will be
  54:  * used.
  55:  *
  56:  * @author Aaron M. Renn (arenn@urbanophile.com)
  57:  * @author Eric Blake (ebb9@email.byu.edu)
  58:  * @since 1.1
  59:  */
  60: public final class Permissions extends PermissionCollection
  61:   implements Serializable
  62: {
  63:   /**
  64:    * Compatible with JDK 1.1+.
  65:    */
  66:   private static final long serialVersionUID = 4858622370623524688L;
  67: 
  68:   /**
  69:    * Holds instances of <code>AllPermission</code>.
  70:    *
  71:    * @serial the permission collection for AllPermission
  72:    */
  73:   private PermissionCollection allPermission;
  74: 
  75:   // Package-private to avoid a trampoline.
  76:   /**
  77:    * This is the <code>Hashtable</code> that contains our collections.
  78:    *
  79:    * @serial maps Class to PermissionCollection
  80:    */
  81:   final Hashtable perms = new Hashtable();
  82: 
  83:   /**
  84:    * This method initializes a new instance of <code>Permissions</code>.
  85:    */
  86:   public Permissions()
  87:   {
  88:   }
  89: 
  90:   /**
  91:    * This method adds a new <code>Permission</code> to this collection.  It
  92:    * will be stored in a <code>PermissionCollection</code> of the appropriate
  93:    * type, as determined by calling <code>newPermissionCollection</code> on
  94:    * the specified permission (if an appropriate collection does not already
  95:    * exist). If this object does not specify a particular type of collection,
  96:    * a default collection, which stores in permissions in a hash table, will
  97:    * be used.
  98:    *
  99:    * @param perm the <code>Permission</code> to add
 100:    * @throws SecurityException if this collection is marked as read only
 101:    */
 102:   public void add(Permission perm)
 103:   {
 104:     if (isReadOnly())
 105:       throw new SecurityException("PermissionCollection is read only");
 106:     if (perm instanceof AllPermission)
 107:       {
 108:         if (allPermission == null)
 109:           {
 110:             allPermission = perm.newPermissionCollection();
 111:             allPermission.add(perm);
 112:             perms.put(perm.getClass(), allPermission);
 113:           }
 114:       }
 115:     else
 116:       {
 117:         PermissionCollection pc
 118:           = (PermissionCollection) perms.get(perm.getClass());
 119:         if (pc == null)
 120:           {
 121:             pc = perm.newPermissionCollection();
 122:             if (pc == null)
 123:               pc = new PermissionsHash();
 124:             perms.put(perm.getClass(), pc);
 125:           }
 126:         pc.add(perm);
 127:       }
 128:   }
 129: 
 130:   /**
 131:    * This method tests whether or not the specified <code>Permission</code>
 132:    * is implied by this <code>PermissionCollection</code>.
 133:    *
 134:    * @param perm the <code>Permission</code> to test
 135:    * @return true if the specified permission is implied by this
 136:    */
 137:   public boolean implies(Permission perm)
 138:   {
 139:     if (allPermission != null)
 140:       return true;
 141:     PermissionCollection pc
 142:       = (PermissionCollection) perms.get(perm.getClass());
 143:     return pc == null ? false : pc.implies(perm);
 144:   }
 145: 
 146:   /**
 147:    * This method returns an <code>Enumeration</code> which contains a
 148:    * list of all <code>Permission</code> objects contained in this
 149:    * collection.
 150:    *
 151:    * @return an <code>Enumeration</code> of this collection's elements
 152:    */
 153:   public Enumeration<Permission> elements()
 154:   {
 155:     return new Enumeration()
 156:     {
 157:       Enumeration main_enum = perms.elements();
 158:       Enumeration sub_enum;
 159: 
 160:       public boolean hasMoreElements()
 161:       {
 162:         if (sub_enum == null)
 163:           {
 164:             if (main_enum == null)
 165:               return false;
 166:             if (! main_enum.hasMoreElements())
 167:               {
 168:                 main_enum = null;
 169:                 return false;
 170:               }
 171:             PermissionCollection pc =
 172:               (PermissionCollection) main_enum.nextElement();
 173:             sub_enum = pc.elements();
 174:           }
 175:         if (! sub_enum.hasMoreElements())
 176:           {
 177:             sub_enum = null;
 178:             return hasMoreElements();
 179:           }
 180:         return true;
 181:       }
 182: 
 183:       public Object nextElement()
 184:       {
 185:         if (! hasMoreElements())
 186:           throw new NoSuchElementException();
 187:         return sub_enum.nextElement();
 188:       }
 189:     };
 190:   }
 191: 
 192:   /**
 193:    * Implements the permission collection for all permissions without one of
 194:    * their own, and obeys serialization of JDK.
 195:    *
 196:    * @author Eric Blake (ebb9@email.byu.edu)
 197:    */
 198:   private static final class PermissionsHash extends PermissionCollection
 199:   {
 200:     /**
 201:      * Compatible with JDK 1.1+.
 202:      */
 203:     private static final long serialVersionUID = -8491988220802933440L;
 204: 
 205:     /**
 206:      * Hashtable where we store permissions.
 207:      *
 208:      * @serial the stored permissions, both as key and value
 209:      */
 210:     private final Hashtable perms = new Hashtable();
 211: 
 212:     /**
 213:      * Add a permission. We don't need to check for read-only, as this
 214:      * collection is never exposed outside of Permissions, which has already
 215:      * done that check.
 216:      *
 217:      * @param perm the permission to add
 218:      */
 219:     public void add(Permission perm)
 220:     {
 221:       perms.put(perm, perm);
 222:     }
 223: 
 224:     /**
 225:      * Returns true if perm is in the collection.
 226:      *
 227:      * @param perm the permission to check
 228:      * @return true if it is implied
 229:      */
 230:     // FIXME: Should this method be synchronized?
 231:     public boolean implies(Permission perm)
 232:     {
 233:       Enumeration elements = elements();
 234: 
 235:       while (elements.hasMoreElements())
 236:         {
 237:           Permission p = (Permission)elements.nextElement();
 238:           if (p.implies(perm))
 239:             return true;
 240:         }
 241:       return false;
 242:     }
 243: 
 244:     /**
 245:      * Return the elements.
 246:      *
 247:      * @return the elements
 248:      */
 249:     public Enumeration elements()
 250:     {
 251:       return perms.elements();
 252:     }
 253:   } // class PermissionsHash
 254: } // class Permissions