When a form is submitted the only thing sent to the server is strings: unless the server side knows how to convert these strings into actual objects you'll not get what you expect.
There are several options, including (a) convert the string representation of the list into an actual List and (b) store the list in session scope. S2's type conversion may help with (a), depending on the string representation of the list--which is what you'll get by putting the list into an <s:hidden...> tag.
I agree. Here's the link: http://ej-technologies/jprofiler - if it wasn't for jprofiler, we would need to
run our stuff on 16 servers instead of 3.
subject: sending a list from jsp to action class hidden