Java constants in JSP

Question

I have a class that defines the names of various constants, e.g.

class Constants {
    public static final String ATTR_CURRENT_USER = "current.user";
}

I would like to use these constants within a JSP without using Scriptlet code such as:

<%@ page import="com.example.Constants" %>
<%= Constants.ATTR_CURRENT_USER %>

There appears to be a tag in the Apache unstandard taglib that provides this functionality. However, I cannot find any way to download this taglib. I'm beginning to wonder if it's been deprecated and the functionality has been moved to another (Apache) tag library?

Does anyone know where I can get this library, or if it's not available, if there's some other way I can access constants in a JSP without using scriptlet code?

Cheers, Don

Solution 1

On application startup, you can add the Constants class to the servletContext and then access it in any jsp page

servletContext.setAttribute("Constants", com.example.Constants);

and then access it in a jsp page

<c:out value="${Constants.ATTR_CURRENT_USER}"/>

(you might have to create getters for each constant)

Solution 2

Turns out there's another tag library that provides the same functionality. It also works for Enum constants.

Solution 3

Looks like a duplicate of accessing constants in JSP (without scriptlet)

My answer was:

Static properties aren't accessible in EL. The workaround I use is to create a non-static variable which assigns itself to the static value.

public final static String MANAGER_ROLE = 'manager';
public String manager_role = MANAGER_ROLE;

I use lombok to generate the getter and setter so that's pretty well it. Your EL looks like this:

${bean.manager_role}

Full code at https://rogerkeays.com/access-java-static-methods-and-constants-from-el

Comments

[Dónal]

If you could rewrite this without using Scriptlet, you will have answered my question.

[Dónal]

I really want to avoid creating getters for each constant

[nhthai]

The setAttribute of servletContext function receive Object as value parameter. Are you sure we can transfer com.example.Constants?

[Vasil Valchev]

where is "application startup"?