Re: Correct Prepopulate Method

[Jesse Clark]

Joel,
Here is a short description from the FAQ that starts to describe the 
alternative that Jack mentioned below: 
http://struts.apache.org/faqs/newbie.html#prepopulate.

This approach basically means that you end up with two actions per 
form/jsp which will increase your maintenance work a little but it 
provides clean entry points into the work flow and clearly illustrates 
what responsibilities an action has by its naming scheme. In the FAQ 
their example actions are called /editFoo and /saveFoo but when I use 
this approach I usually name my action DisplayFooAction and 
ProcessFooAction where Foo indicates the primary function of the 
jsp/form that these actions handle, i.e DisplayEditProfileAction and 
ProcessEditProfileAction for my editProfile.jsp and EditProfileForm.

Then the DisplayFooAction is responsible for gathering the data needed 
to prepopulate the Form from the business service, populating the Form 
and placing it in scope for the jsp. I request that a business service 
prepare the View necessary for the Foo page and then either, populate 
the Form from POJOs in the view or use collections from the view 
directly in the jsp to populate drop-down lists & etc. The Form is 
already available to you in the Action because it is declared in the 
action mapping for both the DisplayFoo and ProcessFoo actions.

Just to qualify my advice, I am still relatively new to this myself and 
this approach seemed like the simplest way to go for now, but I kinda 
feel like having 2 actions per page might end up being too much extra 
baggage and there might be other implications of which I am not yet aware.

Hope this helps, anyhow,
-Jesse
Schuster Joel M Contr ESC/NDC wrote:
Ok, I understand. I'm just really trying to understand this.
http://resonus.net/wiki/uploads/strutsq.jpg
Here's a link to a little picture that I put together because that happens
to be how I think.
Please tell me what I'm missing in my understanding of what struts is all
about. 

1. Standard login process.
        a) request to website from browser, we redirect to the login.jsp via
an action or forward.
        b) Submit is clicked and system encapsulates the data from the
request into a form which is then given to the action.execute which
        c) then determines if the values are correct and forwards to the
right place depending.
2. Now, If I want to have the main menu simply go from one screen to another
then I have a link. But the second screen needs to be 'populated' (for lack
of a better word) with data. 

3. To do it the struts 'way' is to link to an action instead. This action
fills the framework provided form (because it is defined in the mapping) and
forwards to the edit screen.
4. The update action uses the same form which is now filled with changed
values from the jsp.
--- I keep getting the impression that I've missed something in my
understanding of how and more importantly why --- I want to understand, not
just do things blindly.
I understand that the ActionForm is intended to STORE and VALIDATE
USER-ENTERED data (off the struts page)... but then there seems to be a big
hole in the functionality of struts. How do you get to the point of having a
person select inventory and purchase it if you can't first display that
inventory?
- Joel
-----Original Message-----
From: Dakota Jack [mailto:[EMAIL PROTECTED] 
Sent: Friday, March 11, 2005 12:02 PM
To: Struts Users Mailing List
Subject: Re: Correct Prepopulate Method

I may be wrong, Joel, but I think Joe and Hubert are thinking of you
instantiating a form that is not listed in your action mapping.  You
can readily figure out why they think this way.  You can, as you seem
to want to, avoid this complication that actually sort of takes you
out of the reason for the Struts framework by having your ActionForm
encompass the data in both the "pre-Action" and "post-Action" JSP/HTML
forms.
Jack
On Fri, 11 Mar 2005 11:57:33 -0700, Schuster Joel M Contr ESC/NDC
<[EMAIL PROTECTED]> wrote:
 

I've been looking into the RequestProcessor and RequestUtils classes and
   

it
 

looks like as long as my action mapping specifies a name, even on a setup
action goes through the same process... calling createActionForm().
Thus there is no reason to go through my own ModuleConfig again.
-----Original Message-----
From: Hubert Rabago [mailto:[EMAIL PROTECTED]
Sent: Friday, March 11, 2005 10:13 AM
To: Struts Users Mailing List
Subject: Re: Correct Prepopulate Method
On Fri, 11 Mar 2005 09:50:59 -0700, Schuster Joel M Contr ESC/NDC
<[EMAIL PROTECTED]> wrote:
   

I'm not sure I understand the need for the moduleConfig and such for
creating the DynaActionForm.
     

The FormBeanConfig object provides access to the createActionForm()
method.  That's the object you actually need.  You can get to that
through the ModuleConfig for the current module.
   

If we've specified the name="myForm" in the action config then shouldn't
     

the
   

form coming into the execute be and empty version of my form? Thus
     

allowing:
   

    execute( ActionMapping mapping, ActionForm form ... {
           DynaActionForm myForm = (DynaActionForm) form;
    }
(As a matter of fact I know this works :))
     

This is true when you're in the action to which the form was
submitted.  In the example I gave, this would be the /submitForm
action.  In a setup action, this mapping may not be available or may
be referring to a different form altogether.
   

Also, using
request.getSession().setAttribute("myForm", myForm);
is exactly the issue. Although it then allows the follow up jsp to gain
access to the formbean during form(html) creation it doesn't determine
     

how
 

then to remove the form from the session except by explicit removal in
     

the
 

final update/submit action unless you config the submit as request scope
only. But that doesn't actually remove the formbean from the session
     

scope
 

that we added it into... it just copies it into the request scope too.
--- so back to sqare one. :P
     

You can specify which scope you want the form bean to be in (read the
bottom of my prev email).  Struts uses session scope by default, which
is why that's what I mentioned first.  You can choose to use request
scope.
hth,
Hubert
   

-----Original Message-----
From: Hubert Rabago [mailto:[EMAIL PROTECTED]
Sent: Friday, March 11, 2005 9:36 AM
To: Struts Users Mailing List
Subject: Re: Correct Prepopulate Method
You would usually do prepopulation in a setup form.  Which scope you
place the form in depends on how you configure the action that the
form will be submitted to.  For example, if you have "/showPage.do"
and "/submitForm.do", where submitForm is configured as:
<action path="/submitForm" name="myForm" ...>....</action>
Then in the action for showPage, you'd:
   ModuleConfig moduleConfig =
ModuleUtils.getInstance().getModuleConfig(request);
   FormBeanConfig formBeanConfig =
moduleConfig.findFormBeanConfig("myForm");
   DynaActionForm myForm = (DynaActionForm)
formBeanConfig.createActionForm(getServlet());
   myForm.set("propName",propValue);
   request.getSession().setAttribute("myForm", myForm);
If you want to use request scope, change /submitForm to:
<action path="/submitForm" name="myForm"
     

scope="request"...>....</action>
 

then in showPage:
   request.setAttribute("myForm", myForm);
Hubert
     

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