Source for java.lang.reflect.AccessibleObject

   1: /* java.lang.reflect.AccessibleObject
   2:    Copyright (C) 2001, 2005, 2006  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: import java.lang.annotation.Annotation;
  42: 
  43: /**
  44:  * This class is the superclass of various reflection classes, and
  45:  * allows sufficiently trusted code to bypass normal restrictions to
  46:  * do necessary things like invoke private methods outside of the
  47:  * class during Serialization.  If you don't have a good reason
  48:  * to mess with this, don't try. Fortunately, there are adequate
  49:  * security checks before you can set a reflection object as accessible.
  50:  *
  51:  * @author Tom Tromey (tromey@cygnus.com)
  52:  * @author Eric Blake (ebb9@email.byu.edu)
  53:  * @see Field
  54:  * @see Constructor
  55:  * @see Method
  56:  * @see ReflectPermission
  57:  * @since 1.2
  58:  * @status updated to 1.5
  59:  */
  60: public class AccessibleObject
  61:     implements AnnotatedElement
  62: {
  63:   /**
  64:    * True if this object is marked accessible, which means the reflected
  65:    * object bypasses normal security checks.
  66:    */
  67:   // default visibility for use by inherited classes
  68:   boolean flag = false;
  69: 
  70:   /**
  71:    * Only the three reflection classes that extend this can create an
  72:    * accessible object.  This is not serializable for security reasons.
  73:    */
  74:   protected AccessibleObject()
  75:   {
  76:   }
  77: 
  78:   /**
  79:    * Return the accessibility status of this object.
  80:    *
  81:    * @return true if this object bypasses security checks
  82:    */
  83:   public boolean isAccessible()
  84:   {
  85:     return flag;
  86:   }
  87: 
  88:   /**
  89:    * Convenience method to set the flag on a number of objects with a single
  90:    * security check. If a security manager exists, it is checked for
  91:    * <code>ReflectPermission("suppressAccessChecks")</code>.<p>
  92:    *
  93:    * It is forbidden to set the accessibility flag to true on any constructor
  94:    * for java.lang.Class. This will result in a SecurityException. If the 
  95:    * SecurityException is thrown for any of the passed AccessibleObjects,
  96:    * the accessibility flag will be set on AccessibleObjects in the array prior 
  97:    * to the one which resulted in the exception.
  98:    *
  99:    * @param array the array of accessible objects
 100:    * @param flag the desired state of accessibility, true to bypass security
 101:    * @throws NullPointerException if array is null
 102:    * @throws SecurityException if the request is denied
 103:    * @see SecurityManager#checkPermission(java.security.Permission)
 104:    * @see RuntimePermission
 105:    */
 106:   public static void setAccessible(AccessibleObject[] array, boolean flag)
 107:   {
 108:     checkPermission();
 109:     for (int i = 0; i < array.length; i++)
 110:       array[i].secureSetAccessible(flag);
 111:   }
 112: 
 113:   /**
 114:    * Sets the accessibility flag for this reflection object. If a security
 115:    * manager exists, it is checked for
 116:    * <code>ReflectPermission("suppressAccessChecks")</code>.<p>
 117:    *
 118:    * It is forbidden to set the accessibility flag to true on any constructor for 
 119:    * java.lang.Class. This will result in a SecurityException.
 120:    *
 121:    * @param flag the desired state of accessibility, true to bypass security
 122:    * @throws NullPointerException if array is null
 123:    * @throws SecurityException if the request is denied
 124:    * @see SecurityManager#checkPermission(java.security.Permission)
 125:    * @see RuntimePermission
 126:    */
 127:   public void setAccessible(boolean flag)
 128:   {
 129:     checkPermission();
 130:     secureSetAccessible(flag);
 131:   }
 132: 
 133:   /**
 134:    * Performs the specified security check, for
 135:    * <code>ReflectPermission("suppressAccessChecks")</code>.
 136:    *
 137:    * @throws SecurityException if permission is denied
 138:    */
 139:   private static void checkPermission()
 140:   {
 141:     SecurityManager sm = System.getSecurityManager();
 142:     if (sm != null)
 143:       sm.checkPermission(new ReflectPermission("suppressAccessChecks"));
 144:   }
 145: 
 146:   /**
 147:    * Performs the actual accessibility change, this must always be invoked
 148:    * after calling checkPermission.
 149:    *
 150:    * @param flag the desired status
 151:    * @throws SecurityException if flag is true and this is a constructor
 152:    * for <code>java.lang.Class</code>.
 153:    */
 154:   private void secureSetAccessible(boolean flag)
 155:   {
 156:     if (flag &&
 157:         (this instanceof Constructor
 158:           && ((Constructor) this).getDeclaringClass() == Class.class))
 159:       throw new SecurityException("Cannot make object accessible: " + this);
 160:     this.flag = flag;
 161:   }
 162: 
 163:   public <T extends Annotation> T getAnnotation(Class<T> annotationClass)
 164:   {
 165:     throw new AssertionError("Subclass must override this method");
 166:   }
 167: 
 168:   public Annotation[] getAnnotations()
 169:   {
 170:     return getDeclaredAnnotations();
 171:   }
 172: 
 173:   public Annotation[] getDeclaredAnnotations()
 174:   {
 175:     throw new AssertionError("Subclass must override this method");
 176:   }
 177: 
 178:   public boolean isAnnotationPresent(Class<? extends Annotation> annotationClass)
 179:   {
 180:     return getAnnotation(annotationClass) != null;
 181:   }
 182: }