Source for java.security.PermissionCollection

   1: /* PermissionCollection.java -- A collection of permission objects
   2:    Copyright (C) 1998, 2001, 2002, 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: package java.security;
  39: 
  40: import java.io.Serializable;
  41: import java.util.Enumeration;
  42: 
  43: /**
  44:  * This class models a group of Java permissions.  It has convenient
  45:  * methods for determining whether or not a given permission is implied
  46:  * by any of the permissions in this collection.
  47:  *
  48:  * <p>Some care must be taken in storing permissions.  First, a collection of
  49:  * the appropriate type must be created.  This is done by calling the
  50:  * <code>newPermissionCollection</code> method on an object of the
  51:  * permission class you wish to add to the collection.  If this method
  52:  * returns <code>null</code>, any type of <code>PermissionCollection</code>
  53:  * can be used to store permissions of that type.  However, if a
  54:  * <code>PermissionCollection</code> collection object is returned, that
  55:  * type must be used.
  56:  *
  57:  * <p>A <code>PermissionCollection</code> returned by the
  58:  * <code>newPermissionCollection</code> method in a subclass of
  59:  * <code>Permission</code> is a homogeneous collection.  It only will
  60:  * hold permissions of one specified type - instances of the class that
  61:  * created it.  Not all <code>PermissionCollection</code> subclasses
  62:  * have to hold permissions of only one type however.  For example,
  63:  * the <code>Permissions</code> class holds permissions of many types.
  64:  *
  65:  * <p>Since the <code>newPermissionCollection</code> in <code>Permission</code>
  66:  * itself returns <code>null</code>, by default a permission can be stored
  67:  * in any type of collection unless it overrides that method to create its
  68:  * own collection type.
  69:  *
  70:  * @author Aaron M. Renn (arenn@urbanophile.com)
  71:  * @author Eric Blake (ebb9@email.byu.edu)
  72:  * @see Permission
  73:  * @see Permissions
  74:  * @since 1.1
  75:  * @status updated to 1.4
  76:  */
  77: public abstract class PermissionCollection implements Serializable
  78: {
  79:   /**
  80:    * Compatible with JDK 1.1+.
  81:    */
  82:   private static final long serialVersionUID = -6727011328946861783L;
  83: 
  84:   /**
  85:    * Indicates whether or not this collection is read only.
  86:    *
  87:    * @serial if the collection is read-only
  88:    */
  89:   private boolean readOnly;
  90: 
  91:   /**
  92:    * Create a new collection.
  93:    */
  94:   public PermissionCollection()
  95:   {
  96:   }
  97: 
  98:   /**
  99:    * 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