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From Ted Husted <hus...@apache.org>
Subject Re: Wizard pages in Struts design question
Date Sun, 21 Sep 2003 14:59:58 GMT
To prevent repopulation of an ActionForm's properties, you just need to 
provide a property that observes that status of another property that 
indicates whether the form is readonly or not. So, instead of just doing

this.property = property

you have

if (mutable) this.property = property

Or do something more sophisticated, like have it look at the page number 
and then decide whether to set itself or not.

Though, IMHO, the behavior for a step is so complicated that you want to 
put it in its own action, it should probably be outside of Struts all 
together, and part of the business logic layer.

(This is why chaining is frowned upon. It's a red flag that indicates 
business logic is creeping into your Action classes. When the business 
logic is sufficiently fine-grained, you should just be able to whatever 
you need to do from whatever Action you happen to be in. As work 
progresses on Commons Chain, I think this will provide a solution many 
people will prefer to chaining Struts Action).

I haven't had a chance to abstract it into a standard class, but here's 
a wizard Action that I'm working with now. It submits back to the same 
class, but uses a dispatch action so that if a step needs more behavior 
it can be encapsulated that way.

http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/wqdata/wqdata/src/java/apps/cpu/us_ok_deq_wqdata/cpu/WizardAction.java

The steps are laid out as ActionForwards to the instant ActionMapping, 
making it very easy to rewrite.

-Ted.

Erez Efrati wrote:
> I read the HowTo write a wizard on the Struts web-site but I wasn't
> really happy with the solution, and I am looking for a better one. I
> came up with another way and I would appreciate your comments. 
> 
> The design consists of: 
> - The 'form' is a session scope form
> - WizardAction class (a DispatchAction based) with following methods:
> 	* init () - starting the wizard and redirect to the first page
> 	* finish () - (or save()) finish the wizard and save the
> information 			  in the form using some business logic
> delegate.
> 	
> - Each Page or step in the wizard is a separate Action class, extending
> a 	WizrardBaseAction (a DispatchAction based) which contains some
> shared 	methods.
> 
> 	For example: Page1Action extends WizardBaseAction {
> 
> 			// initializes the page (done only on first
> encounter)
> 			ActionForward init (mapping,...) throws
> Exception;
> 			ActionForward back (mapping,...) throws
> Exception;
> 			ActionForward next (mapping,...) throws
> Exception;				ActionForward finish
> (mapping,...) throws Exception;
> 	}		
> 
> - Each page/step has a separate action-mapping item in the configuration
> with local forwards for : 'back' (if not the first page), 'next',
> 'finish' (if allowed from that page).
> 
>  I apologize for not sketching the whole idea down to the last bit but I
> hope you get the picture. 
> 
> Only problem is that this design touches the question of chaining
> actions verses forward redirection (not just dispatching). 
> 
> For example the Page1Action.next() does the following:
> 	1. validate the page
> 	2. perform whatever processing required
> 	3. return the next action to forward to (redirect or chain with
> all 	its illness..)
> 
> In my opinion (humble one of course :) having such a separation keeping
> each step in its own class is better and clearer design than having them
> all in the same Action class. 
> 
> Isn't there a way to prevent the reset + pre-population of the form done
> while chaining actions? Furthermore, is it so bad to redirect between
> actions? 
> 
> Thanks in advance,
> Erez
> 
> 
> 
> 
> 
> 
>  
> 
> 
> 
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> 
> 

-- 
Ted Husted,
   Junit in Action  - <http://www.manning.com/massol/>,
   Struts in Action - <http://husted.com/struts/book.html>,
   JSP Site Design  - <http://www.amazon.com/exec/obidos/ISBN=1861005512>.

"Get Ready, We're Moving Out!!" - <http://www.clark04.com>



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