Think you might have solved the above problem with the help of SimpleTagSupport.
I would like to show you the same with TagSupport:
In my application there are 2 jsp files. One of them captures input (two numbers) from the user, keeps them in request Scope and forwards it to result page where i display the result using my <gopi:add/> tag.
for that you need to change the following in the above addition of 2 numbers example: