Nulls in OGNL expressions

["Julio C. Rivera" <ju...@ya.com>]

Hi!

I have a problem using OGNL.
When I access to, for instance, expr = prop1.prop2.prop3 I want
   if (prop1 == null)  then expr == null
   if ((prop1 != null) && (prop2 == null))  then expr == null
   if ((prop1 != null) && (prop2 != null) && (prop3 == null))  then expr == 
null
In a nutshell, if any property in the graph is null, then it returns null 
(NEVER a NullPointException).

I have a NullHandler like the following:

   public class DefaultNullHandler extends ObjectNullHandler {

     public Object nullPropertyValue(Map context,Object target,Object 
property) {
       return new HashMap();
     }

     public java.lang.Object nullMethodResult(Map context,Object 
target,String methodName,List args) {
       return new HashMap();
     }
   }

It works fine if I ask for prop1.prop2 (and prop1 is null), but if I do 
that, when I ask for prop1 property, and prop1 is null, I get a empty Map, 
when I would like to get a null.

A NullHandler like the following solves my problem:

   public class DefaultNullHandler extends ObjectNullHandler {

     public Object nullPropertyValue(Map context,Object target,Object 
property) {
       if (property is the last property in the expression chain) <-- HOW 
CAN I DO IT?
          return null
          else return new HashMap();
     }

     public java.lang.Object nullMethodResult(Map context,Object 
target,String methodName,List args) {
       if (methodName is the last method in the expression chain) <-- HOW 
CAN I DO IT?
                 return null
          else return new HashMap();
     }
   }

Any suggestion?

( I think would be useful a "NeverNullPointerExceptionNullHandler" in OGNL. 
I think its a common need.)

Thanks in advance.
   Julio.