Action vs. DispatchAction and the input parameter

["Lafredo, Stephen" <st...@merck.com>]

Hello,

I decided to try a DispatchAction in my application but quickly ran into a
question.

Background:

 As everyone knows, we typically define an Action class as,

  <action path="/foo"
          type="com.action.Foo"
         scope="request"
          name="fooForm"
         input="foo">   <!-- using Tiles -->
    <forward name="success" path="foo-success"/>
  </action>
 
 similarly, we define a DispactionClass as,

  <action path="/bar"
     parameter="method"
          type="com.action.Bar"
         scope="request"
          name="fooBar"
         input="bar">
    <forward name="input"  path="bar"/>
    <forward name="add"    path="add-success"/>
    <forward name="update" path="update-success"/>
  </action>

Question:

 When using an Action class the view specified by the 'input' parameter is
displayed when we invoke the action. For example, http://localhost/foo. Upon
successful completion of the Action we can send the user to the view defined
by the forward element, e.g. foo-success.

 When using a DispatchAction we must specify a parameter identifying the
method we wish to call. For example, http://localhost/bar?method=add. The
problem, I am having is how do I display the DispatchAction's default view
as specified by the 'input' parameter? I want to display this view to
collect information before performing one of the defined actions.

 Unlike an Action class, if I attempt to invoke bar, http://localhost/bar,
w/o specifying a method, reflection fails and an error is displayed.

 I have found two solutions to work around this but they both seem to be
adding more work and confusion to the configuration and I therefore end up
loosing some of the savings gained by using the DispatchAction.

The first solution is to declare another forward element w/in my
DispatchAction declaration to display the form. For example, <forward
name="input" path="bar"/> and then define a NO-OP method in my
DispatchAction class. For example,

   public ActionForward input(ActionMapping mapping
                             ,ActionForm form
                             ,HttpServletRequest request
                             ,HttpServletResponse response)
     throws Exception {

     return mapping.findForward("input");
   }

The second solution is to declare the NO-OP in the struts-config.xml file
and let Struts forward to the view. For example,

    <action path="/bar-input"
         forward="bar"/>

To _me_ these do not seem like optimal solutions.

In the first solution, I am basically re-implementing the functionally
provided to me by Struts in the second solution.

In the second solution, I am adding configurations with confusing naming
conventions to display my input forms w/o invoking my DispatchAction class.

So...

What purpose does the 'input' parameter have when defining a DispatchAction?
None, correct?

Should I only use DispatchActions for GUI(less) actions?

Thanks.

Stephen Lafredo
Merck & Co., Inc.
E: stephen_lafredo@merck.com


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