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

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

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