JavaServer Pages, 3rd Edition

Accessing Scoped Variables in Scripting Code

The term variable is generally used for any dynamic data an application manipulates, but when we talk about JSP and scripting elements, it’s important to be more specific.

JSP custom actions, including the JSTL actions, can expose data through what is called scoped variables, typically named by a var and an optional scope attribute. A scoped variable is an object that lives in one of the JSP scopes: page, request, session, or application. As mentioned earlier, the scopes are actually collections of named object references that correspond to the attributes that the implicit pageContext, request, session, and application objects provide access to.

Another type of variable is a scripting variable. A scripting variable is a variable declared in a JSP scriptlet or declaration, using the language defined for the page (typically Java). To read or manipulate data with scripting code, you need a scripting variable that holds a reference to the object that contains the data.

The distinction between the variable types becomes apparent when you mix actions that expose data only as scoped variables with scripting elements. To use the data exposed by the action in a scripting element, you must first tell the container to create a scripting variable for it and assign it the value of the scoped variable. The easiest way to do this is to use the standard <jsp:useBean> action:

<%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %> <%@ page import="java.util.Date" ...