RE: Passing ActionForm along on the request

Wed, 26 May 2004 09:30:37 -0700

I presume the element that's throwing the NPE is one of the elements that the user cannot change. I presume this because let's say for the sake of argument that all the fields of the ActionForm were on the screen, then what you describe should never happen.

Your dealing with the classic stateless nature problem of the web in general... you can either put it in session (or some other persistent storage on the server) or you can pass the information to the view, which wil pass it with the next request (i.e., hidden form fields, as you alluded to).

Putting any object in request definitively means that it should NOT persist between requests, that's the whole point, so if you have something you need to persist, as you do here, those are your choices basically, either session or data passing between JSPs. If security is an issue you can get into applets or (God forbid!) ActiveX controls, then do all your data passing through them (and this might not even work with applets since they will probably be loading with each page load, so there's no persistence there either, so ActiveX becomes the option, but then your talking IE only, without buggy plug-ins anyway, so really neither is much of an option anyway).


From: "Jeremy Nix" <[EMAIL PROTECTED]>
Reply-To: "Struts Users Mailing List" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Subject: Passing ActionForm along on the request
Date: Wed, 26 May 2004 10:35:41 -0400

Is it possible to call an Action which pre-populates a form, forwards on
to a JSP page which displays the form values for the user to change, and
then submit back to an Action that will contain the form value?  We're
running into a scenario where we prepopulate the Form in 1 action and
set it onto the Request.  The jsp displays some of the values so that
they may be modified, and then submits back to a second action where the
Form is to be populated.  When the form is submitted to the 2nd Action,
the ActionForm is reinitialized, and ends up throwing an exception in
the BeanUtils.populate method because an object on the form is null.
We've found that the scenario works fine when using Sessions, but runs
into issues when using the request.

Here's a sample struts config:

<action
        path="/actions/MyAction"
        type="actions.MyAction"
        name="myActionForm"
        scope="request"
        validate="false">
                <forward name="continue" path="/actions/MyAction.jsp"/>
</action>

<action
        path="/actions/MyActionSubmit"
        type="actions.MyActionSubmit"
        name="myActionForm"
        scope="request"
        input="/actions/MyAction.jsp"
            validate="true">
                <forward name="continue" path="/actions/MyNextAction"/>
</action>

We already have 1 solution (using sessions), but given the fact that
we're going to be working in a load-balanced environment with multiple
Tomcat instances, we are trying to use the session sparingly.

Another solution that I just thought of would be to replicate all the
values of the Form as hidden values on the JSP page so that they would
be repopulated on the submit.  This would be slightly annoying, but is a
viable solution.

My question is, is there another solution that works as clean as
sessions but uses the request?


_________________________________
Jeremy Nix
Senior Application Developer
Southwest Financial Services, LTD.
(513) 621-6699 x1158
www.sfsltd.com



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