src/share/classes/sun/reflect/misc/ReflectUtil.java

*** 142,147 ****
--- 142,181 ----
          } catch (SecurityException e) {
              return false;
          }
          return true;
      }
+ 
+     // Returns true if p is an ancestor of cl i.e. class loader 'p' can 
+     // be found in the cl's delegation chain
+     private static boolean isAncestor(ClassLoader p, ClassLoader cl) {
+         ClassLoader acl = cl;
+         do {
+             acl = acl.getParent();
+             if (p == acl) {
+                 return true;
+             }
+         } while (acl != null);
+         return false;
+     }
+ 
+     /**
+      * Returns true if package access check is needed for reflective
+      * access from a class loader 'from' to classes or members in 
+      * a class defined by class loader 'to'.  This method returns true
+      * if 'from' is not the same as or an ancestor of 'to'.  All code
+      * in a system domain are granted with all permission and so this
+      * method returns false if 'from' class loader is a class loader
+      * loading system classes.  On the other hand, if a class loader
+      * attempts to access system domain classes, it requires package
+      * access check and this method will return true.
+      */
+     public static boolean needsPackageAccessCheck(ClassLoader from, ClassLoader to) {
+         if (from == null || from == to)
+             return false;
+  
+         if (to == null)
+             return true;
+ 
+         return !isAncestor(from, to);
+     }
  }