Jump the hurdles of Struts development

Tips for solving common difficulties in Struts

By Michael Coen and Amarnath Nanduri, JavaWorld.com, 04/18/03

Page 2 of 6

A rule of thumb in naming the ActionForm objects in struts-config.xml is to end the object name with Form, thereby simplifying the maintenance of these forms in session. For example: ReservationForm, SearchUserForm, BankAccountForm, UserProfileForm, and so on.

The code below further clarifies ActionForm(s) management by illustrating a generic menu traversal action with the Action mappings:

 public class MenuAction {
  public ActionForward perform(ActionMapping       _mapping,
                               ActionForm          _form,
                               HttpServletRequest  _request,
                               HttpServletResponse _response)
                                  throws IOException, ServletException {
    // Check end-user permissions whether allowed into the requested     
    // functionality 
    checkIfUserAllowedToProceed(_mapping, _form, _request, _response); 
    // Clean up the session object (this logic is in its own method)
    String formName = null; 
    HttpSession session = _request.getSession();
    Enumeration e = session.getAttributeNames();  
 
    while(e.hasMoreElements()) {
     
      formName = (String)e.nextElement();
      if (formName.endsWith("Form")){
        session.removeAttribute(formName);
      }    
    }
    // Now find out which functionality the end-user wants to go to
    String forwardStr = _request.getParameter("nextFunctionality");
    if (forwardStr != null && forwardStr.trim().length() > 0){
      return _mapping.findForward(forwardStr);
    }
    else {
      return _mapping.findForward("index");
    }
  }  
}

The following Action mapping is an example of how to implement an action based on a menu selection:

<!-- A generic menu action that forwards the user from one 
     functionality to another functionality (after checking permissions)
-->
<action path="/menuAction"
        type="x.y.z.MenuAction"
        input="/menu.jsp">      
  <forward name="create_reservation" path="/actionResv.do"/> 
  <forward name="index"              path="/menu.jsp"/> 
  <forward name="add_person"         path="/actionPerson.do"/> 
  <forward name="logout"             path="/actionLogout.do"/> 
</action>

The example and the mapping are self-explanatory.

Tell me again, how are we related?

Any JSP can have one to many entry points and one to many exit points, depending on the complexity of the page itself. Recognizing these relationships is paramount to understanding and maintaining the complexity of the user interface. We have defined the relationships between a JSP page and an Action class as:

• 1:1 relationship
• 1:N relationship
• N:N relationship

1:1 relationship

In a 1:1 relationship, a user goes from one JSP page to another through an Action class; this facilitates tight coupling between a JSP page and an Action. The only extra overhead is one Action mapping in struts-config.xml. This single Action with only one Action mapping in struts-config.xml can be used to go from one page to another.

Referencing one JSP page directly through another is poor practice; the user's permissions that go to the target JSP page cannot be checked (if applicable). This also leads to maintenance issues. To avoid these issues, always go from one JSP page to another through an Action class: