Re: [Springframework-developer] Form View and Results View on same page issue.

[<wi...@ly...>]

I posted this late last week but didn't get any bites -- maybe I'll try 
a different angle :).  
In short, I believe that the SimpleFormController should be enhanced to 
support posting results back to the originating form page.  The current 
implementation requires implementing classes to know they are returning 
back to the originating form page.  This limits the generic ability of 
wiring up views via IOC and getSuccessView() on SimpleFormHandler.  
Since this is such a common scenario, I was hoping this could be 
addressed prior to the 1.0 release.  Thoughts?

Bill Lyvers


wi...@ly... wrote:

> I recently started using the web framework portion of Spring.  One 
> concept in particular has bitten me a couple of times and I have been 
> unable to determine a best practice.  The concept is how 
> SimpleFormHandler has a different workflow based on whether it is a 
> get request versus a post request.  This concept seemed very intuitive 
> and works fine if the post goes off to a result page.  However, below 
> is a scenario that I believe is quite common and SimpleFormHandler 
> doesn't seem to deal with it very elegantly.  The problem arises when 
> a page displays both a form and the results of a form post on the same 
> page.
>
> Scenario:
> There is item search page with a item search form on the top and a 
> tabular view of the item search results below the search page.
>
> Example Controller:
> public class ItemSearchController extends SimpleFormController {
>    private ItemManager manager;
>    public void setSearchManager(ItemManager manager) {
>        this.manager = manager;
>    }
>    protected Map referenceData(HttpServletRequest request) throws 
> Exception {
>        Map map = new HashMap();
>        map.put( "itemTypes", manager.getItemTypes() );
>        return map;
>    }
>    protected ModelAndView onSubmit(Object object) throws Exception {
>        Item command = (Item)object;
>        return new ModelAndView( getSuccessView(), "items", 
> manager.findItemsByExample( command ));
>    }
> }
>
> So, I request the page via /searchItem.htm which maps 
> ItemSearchController.  The "get" workflow works as usual -- 
> referenceData gets called and the page displays fine.  The user 
> submits a search criteria which then goes through "post" workflow and 
> onSubmit gets called which returns a list of items via ModelAndView.  
> The successView now needs to return to the same page and this time the 
> results will be displayed below the form. However,
>    1. If I forward back to /searchItem.htm, then I end up in an 
> infinite loop because the controller keeps processing it as a post.
>    2. If I forward on to the jsp that displayed the form originally, I 
> will not go through the same workflow as when the page was first 
> loaded and referenceData won't get called. Not too mention that I'll 
> get an binding errors missing exception -- I saw that RC1 tried to 
> address this, but only if you don't override onsubmit.
>
> So, I decided to solve the problem with option 1 and cause the form to 
> realize that the post had already been handled and it must be a "get" 
> request being caused by a forward.  The main reason for this is that 
> the get workflow gets used when entering the page each.  To fix it, I 
> overrode isFormSubmission and set an attribute when a formSubmission 
> was recognized.  If this attribute already exists, it assumes that it 
> is a get request instead. Example:
> protected boolean isFormSubmission(HttpServletRequest 
> httpServletRequest) {
>        Object alreadySubmitted = httpServletRequest.getAttribute( 
> "formSubmission");
>        if (alreadySubmitted != null) {
>            return false;
>        }
>        boolean formSubmission = 
> super.isFormSubmission(httpServletRequest);
>        if( formSubmission ) {
>            httpServletRequest.setAttribute( "formSubmission", 
> Boolean.TRUE );
>        }
>        return formSubmission;
> }
>
>
> I am a surprised that SimpleFormController doesn't deal with this 
> scenario since it is so common or maybe I am missing something and it 
> does.   With the above code you can switch out the success view to go 
> to a seperate result page later by just changing the IOC 
> configuration.   Basically, your controller doesn't really need to 
> know that the results page is the same view as the form view.
>
> I am very curious on how others are dealing with this scenario and if 
> Spring deals with it and I have just overlooked it.
>
> Keep up the good work,
> Bill Lyvers
>
>
>
>
>
>
>
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