You cannot use a custom tag as the attribute of another tag.
vijaya bacina wrote:Is there a way to make this work without using scriptlets?
You never need to use scriptlets. Ever. You just need to set up your tags correctly.
For example, your 'out' tag should have the ability to put its result into a scoped variable, just like <c:out> does. That way, in your other tag, you can just use the EL to express the value as the attribute.