Source for java.lang.reflect.AccessibleObject

   1: /* java.lang.reflect.AccessibleObject
   2:    Copyright (C) 2001, 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.lang.reflect;
  40: 
  41: /**
  42:  * This class is the superclass of various reflection classes, and
  43:  * allows sufficiently trusted code to bypass normal restrictions to
  44:  * do necessary things like invoke private methods outside of the
  45:  * class during Serialization.  If you don't have a good reason
  46:  * to mess with this, don't try. Fortunately, there are adequate
  47:  * security checks before you can set a reflection object as accessible.
  48:  *
  49:  * @author Tom Tromey (tromey@cygnus.com)
  50:  * @author Eric Blake (ebb9@email.byu.edu)
  51:  * @see Field
  52:  * @see Constructor
  53:  * @see Method
  54:  * @see ReflectPermission
  55:  * @since 1.2
  56:  * @status updated to 1.4
  57:  */
  58: public class AccessibleObject
  59: {
  60:   /**
  61:    * True if this object is marked accessible, which means the reflected
  62:    * object bypasses normal security checks.
  63:    */
  64:   // default visibility for use by inherited classes
  65:   boolean flag = false;
  66: 
  67:   /**
  68:    * Only the three reflection classes that extend this can create an
  69:    * accessible object.  This is not serializable for security reasons.
  70:    */
  71:   protected AccessibleObject()
  72:   {
  73:   }
  74: 
  75:   /**
  76:    * Return the accessibility status of this object.
  77:    *
  78:    * @return true if this object bypasses security checks
  79:    */
  80:   public boolean isAccessible()
  81:   {
  82:     return flag;
  83:   }
  84: 
  85:   /**
  86:    * Convenience method to set the flag on a number of objects with a single
  87:    * security check. If a security manager exists, it is checked for
  88:    * <code>ReflectPermission("suppressAccessChecks")</code>.<p>
  89:    *
  90:    * It is forbidden to set the accessibility flag to true on any constructor
  91:    * for java.lang.Class. This will result in a SecurityException. If the 
  92:    * SecurityException is thrown for any of the passed AccessibleObjects,
  93:    * the accessibility flag will be set on AccessibleObjects in the array prior 
  94:    * to the one which resulted in the exception.
  95:    *
  96:    * @param array the array of accessible objects
  97:    * @param flag the desired state of accessibility, true to bypass security
  98:    * @throws NullPointerException if array is null
  99:    * @throws SecurityException if the request is denied
 100:    * @see SecurityManager#checkPermission(java.security.Permission)
 101:    * @see RuntimePermission
 102:    */
 103:   public static void setAccessible(AccessibleObject[] array, boolean flag)
 104:   {
 105:     checkPermission();
 106:     for (int i = 0; i < array.length; i++)
 107:       array[i].secureSetAccessible(flag);
 108:   }
 109: 
 110:   /**
 111:    * Sets the accessibility flag for this reflection object. If a security
 112:    * manager exists, it is checked for
 113:    * <code>ReflectPermission("suppressAccessChecks")</code>.<p>
 114:    *
 115:    * It is forbidden to set the accessibility flag to true on any constructor for 
 116:    * java.lang.Class. This will result in a SecurityException.
 117:    *
 118:    * @param flag the desired state of accessibility, true to bypass security
 119:    * @throws NullPointerException if array is null
 120:    * @throws SecurityException if the request is denied
 121:    * @see SecurityManager#checkPermission(java.security.Permission)
 122:    * @see RuntimePermission
 123:    */
 124:   public void setAccessible(boolean flag)
 125:   {
 126:     checkPermission();
 127:     secureSetAccessible(flag);
 128:   }
 129: 
 130:   /**
 131:    * Performs the specified security check, for
 132:    * <code>ReflectPermission("suppressAccessChecks")</code>.
 133:    *
 134:    * @throws SecurityException if permission is denied
 135:    */
 136:   private static void checkPermission()
 137:   {
 138:     SecurityManager sm = System.getSecurityManager();
 139:     if (sm != null)
 140:       sm.checkPermission(new ReflectPermission("suppressAccessChecks"));
 141:   }
 142: 
 143:   /**
 144:    * Performs the actual accessibility change, this must always be invoked
 145:    * after calling checkPermission.
 146:    *
 147:    * @param flag the desired status
 148:    * @throws SecurityException if flag is true and this is a constructor
 149:    * for <code>java.lang.Class</code>.
 150:    */
 151:   private void secureSetAccessible(boolean flag)
 152:   {
 153:     if (flag &&
 154:         (this instanceof Constructor
 155:           && ((Constructor) this).getDeclaringClass() == Class.class))
 156:       throw new SecurityException("Cannot make object accessible: " + this);
 157:     this.flag = flag;
 158:   }
 159: }