Spring MVC Binding

Question

I am not sure if this is possible, but I need to do some odd binding with Spring MVC. We have to dynamically generate a page which is a precursor to running some reports. Different reports will have different criteria which are available restrict what data is shown on the report.

I was hoping that I could do something like this:

public interface ReportingStrategy extends Serializable {
    public String getReportingCriteria(); //Each subclass will generate the SQL needed
}

public class DateLimitingStrategy implements ReportingStrategy {

    private Date startDate;
    public Date getStartDate() { return startDate; }
    public void setStartDate(Date startDate) { this.startDate = startDate; }

    private Date endDate;
    public Date getEndDate() { return endDate; }
    public void setEndDate(Date endDate) { this.endDate = endDate; }

    public String getReportingCriteria() {
        //Generate SQL for date range (where necessary)
    }
}

public class SortingStrategy impelements ReportingStrategy {
    public String sortValue;
    public String getSortValue() { return this.sortValue; }
    public void setSortValue(String sortValue) { this.sortValue = sortValue; }
}

So it seems like a pretty simple idea.

On my controller side I'd like to be able to bind to a list of these on a post. I'm able to generate the HTML which should make this necessary, but the binding isn't working properly. Here's a basis of my controller:

@RequestMapping(method = RequestMethod.GET) 
public ModelAndView(@RequestParam("reportName") String reportName) {
    ModelAndView mav = new ModelAndView("showReportingStrategies");
    mav.addObject("backingObject", new BackingObject(reportName));
    return mav;
}

@RequestMapping(method = RequestMethod.POST)
public ModelAndView(@ModelAttribute("backingObject") BackingObject bo, BindingResult result) {
    //More logic here   
}

public class BackingObject implements Serializable {
    private List<ReportingStrategy> reportingStrategies;
    public void setReportingStratgies(List<ReportingStrategy> reportingStrategies) {
        this.reportingStrategies = reportingStrategies;
    }
    public List<ReportingStrategy> getReportingStrategies() { return this.reportingStrategies; }
}

Is this even possible by extending PropertyEditorSupport and doing InitBinder magic?

Are the types of reporting strategies known at the time the page is loaded, or is the user choosing them? — Affe
– Affe, Commented Jun 29, 2011 at 19:20
They will be known, just dynamic in that report A might have a date limiting strategy and report B might have both. The constructor for the BackingObject will look them up in the DB (not shown) — Scott
– Scott, Commented Jun 29, 2011 at 19:48

Affe · Accepted Answer · 2011-06-29 20:01:20Z

1

The far and away simplest thing is to use @SessionAttributes to put your backing object on the session. This way the concrete types are present at bind time. The binder doesn't need to be able to figure out what implementer of ReportingStrategy to use, they're already there. The server side state may be an issue for you of course, and if you're using raw MVC without webflow and your application supports multi-tabbed use, you'll need to handle that as always.

answered Jun 29, 2011 at 20:01

Affe

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