Using top object in Struts 2.5

Question

According to s2-026:

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

We used the top object in lots of JSP pages as below (which shows a list of currencyTypes and look up the name from Struts messages):

<s:select name = "selectedCurrencyType" 
          list = "currencyTypes"
       listKey = "top" 
     listValue = "%{getText('acc.currencyType.'+top)}" />

It currently works with struts 2.3.24.1 but according to above comment, will above select box works for 2.5, or we will not have the top reference any more?!

If this is true, please let me know how should we fix above s:select?!

I mean the top object, which represents root of execution context. Will the above select work on 2.5? If not how should we fix it ?! — Alireza Fattahi, Sep 28 '15 at 08:02
@AlirezaFattahi RomanC is asking you which object are you referring to with the `top` keyword. I've supposed it is the current element in an iteration, but it could also be something else so you should be more specific about it — Andrea Ligios, Sep 28 '15 at 08:05
@AlirezaFattahi: These kinds of question are better to ask on S2 mailing lists. — Aleksandr M, Sep 28 '15 at 10:18
@RomanC yes this the current element in iteration same as http://struts.apache.org/docs/iterator.html and http://stackoverflow.com/questions/23494891/struts-2-sselect-with-values-from-resource-bundle thanks !! — Alireza Fattahi, Sep 28 '15 at 12:08
Go back to the toString() way then, if it worked in listValue you're good. — Andrea Ligios, Sep 28 '15 at 13:11
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 `top` — Lukasz Lenart, Oct 01 '15 at 06:03
@LukaszLenart Thanks, please send it as an answer so I can add mark it as answered! — Alireza Fattahi, Oct 01 '15 at 07:03

score 3 · Accepted Answer · answered Oct 01 '15 at 10:46

3

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.

answered Oct 01 '15 at 10:46

Lukasz Lenart

987
7
14

score 1 · Answer 2 · edited May 23 '17 at 12:06

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.

Using top object in Struts 2.5

2 Answers2

Linked