How to access constants in EL?

Question

In my servlet I setup a request attribute with its name coming from another class.

In my JSP I want to access that request attribute using EL but how to tell EL to look for the name of the request attribute as a constant field of another class?

This is my example:

I have a class RoleDTO:

public class RoleDTO implements Serializable {
   private int roleId;
   private String roleDescription;

   public int getRoleId() {
      return roleId;
   }
   public void setRoleId(int roleId) {
      this.roleId = roleId;
   }
   public String getRoleDescription() {
      return roleDescription;
   }
   public void setRoleDescription(String roleDescription) {
      this.roleDescription = roleDescription;
   }
}

I have a class RoleConstant which has a constant defined:

public class RoleConstant {
   public static final String ROLE_LIST = "roleDTOs";
}

I have a servlet RoleServlet where I am creating a List of RoleDTO objects and setting it to request object as an attribute with the attribute name same as the constant defined in RoleConstant class, before forwarding to role.jsp:

public class RoleServlet extends HttpServlet {
   protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
      List<RoleDTO> roleDTOList = new ArrayList<RoleDTO>();
      RoleDTO roleDTO1 = new RoleDTO();
      roleDTO1.roleId = 1;
      roleDTO1.roleDescription = "Administrator";
      roleDTOList.add(roleDTO1);
      RoleDTO roleDTO2 = new RoleDTO();
      roleDTO2.roleId = 2;
      roleDTO2.roleDescription = "Guest";
      roleDTOList.add(roleDTO2);
      request.setAttribute(RoleConstant.ROLE_LIST, roleDTOList);
      RequestDispatcher view = request.getRequestDispatcher("role.jsp");
      view.forward(request, response);
   }
}

In the role.jsp I access the request attribute by name to get the List of RoleDTO objects and enable or disable a <select> html element based on its contents:

<c:if test="${empty Test05Constant.ATTRIBUTE_ROLE_LIST}">
   <select id="select_role" name="select_role" disabled="disabled">
   </select>
</c:if>

<c:if test="${not empty Test05Constant.ATTRIBUTE_ROLE_LIST}">
   <select id="select_role" name="select_role">
   </select>
</c:if>

But the above code does not work and the <select> html element is shown as disabled even when there is List of RoleDTO objects.

If I hardcode the request attribute name like this:

<c:if test="${empty roleDTOs}">
   <select id="select_role" name="select_role" disabled="disabled">
   </select>
</c:if>

<c:if test="${not empty roleDTOs}">
   <select id="select_role" name="select_role">
   </select>
</c:if>

then it works and the <select> html element is shown as enabled when there is List of RoleDTO objects

I cannot do hardcoding in this case. Can anybody tell me how to get this working?

Thanks

Answer 1

We cannot access static variables in jstl. For workaround we can assign static variable to non-static variable and then try to access it. For reference you can go through For workaround please go through or another way I can think of is accessing through setter methods.