Jakarta Struts Cookbook

2.3. Using Constants on JSPs

Problem

Without resorting to scriptlets, you want to use application constants— public static fields defined in Java classes—on a JSP page.

Solution

Use the bind tag provided by the Jakarta Taglibs unstandard tag library to create a JSTL variable containing the value of the constant field:

<%@ taglib uri="http://jakarta.apache.org/taglibs/unstandard-1.0" prefix="un" %>
<un:bind var="constantValue"
        type="com.foo.MyClass"
       field="SOME_CONSTANT"/>
<bean:write name="constantValue"/>

Discussion

A lot of teams put hard work into avoiding hard-coded String literals in their Java classes by using public static fields (constants). Unfortunately, neither Struts nor JSP provide a means to access these constants from a JSP page without resorting to JSP scriptlet like the following:

<%= com.foo.MyClass.SOME_CONSTANT %>

However, many development teams ban, or at least frown on scriptlet use on JSP pages.

Warning

Scriptlets (<% . . . %>) and runtime expressions (<%= . . . %>) place Java code directly onto a JSP page. They are not inherently evil, but they can lead your development down a slippery slope by turning your JSP pages into a tangled brittle mass of intermixed HTML, JSP, and Java code. Find solutions that don't require you to use scriptlets. You'll find—particularly with the introduction of JSTL—that you can always find a way around the dreaded scriptlet.

The Solution provides a way around this quandary through the use of a custom JSP tag, the un:bind tag. This tag ...