Using 'top' object in Struts 2.5

Question

According to http://struts.apache.org/docs/s2-026.html :

Support for expression using top will be dropped in upcoming Struts version 2.5!

Answer 1

What I found in this documentation and what I use in my example Passing parameters to action through ModelDriven in Struts 2 the top object is a element of the CompaundRoot. And this class has a cutStack() method that is mentioned in

With expression like [0] ... [3] etc. Struts 2 will cut the stack and still return back a CompoundRoot object. To get the top of that particular stack cut, use 0.top.

The last expression is a typo for [xxx].top where xxx is the index of the CompoundRoot object. And this object could be referenced as [xxx]. It is a top object cut to the xxx index.

Answer 2

Support for top object was added to support internal operations, it shouldn't be used by users (yes, expressing that in docs was a bad idea :( )

Anyway, looks like we must prepare a migration path or keep support for the top object.