Unless you have a good reason for it to stay around for the long haul, you should be placing it in request scope. Putting it in session scope is a good way to keep it around for longer than the current request, but you should only do that when necessary. Using application scope (the servlet context) should only be done for information that needs to be shared across al users.
You really should learn to use the EL rather than scriptlets and scriptlet expressions, but your syntax: is a scriptlet statement. In order to emit a value, you need to use a scriptlet expression, whose syntax would be:
However, again, you should look into modernizing your JSP knowledge with the Expression language (EL).