I was just suggesting to you that the intellisense / code assist works within that tag. The <%= %> is normal JSP expression. I was merely using it as an example of what will work then you can put then you can remove after. This was to get around the limitation with being able to do in the EL ${}.
Ref.:
http://www.ibm.com/developerworks/java/library/j-jstl0211.html#N100A9
From my understanding, some IDE's like IntelliJ can do this, but as far as I know they are paid products.