How do you configure a controller-specific field formatter with Spring MVC?

Question

I have a data type in my application called Foo which looks something like this:

public class Foo {
  // synthetic primary key
  private long id; 

  // unique business key
  private String businessKey;

  ...
}

This type is used in many forms throughout the web application and typically you want to convert it back and forth using the id property so I have implemented a Spring3 Formatter that does that and registered that formatter with the global Spring conversion service.

However, I have one form use case where I want to convert using the businessKey instead. It's easy enough to implement a Formatter to do that, but how do I tell Spring to use that formatter for just this specific form?

I found a document at http://static.springsource.org/spring/previews/ui-format.html which has a section on registering field-specific formatters (see 5.6.6 all the way at the bottom) which offers this example:

@Controller
public class MyController {
  @InitBinder
  public void initBinder(WebDataBinder binder) {
    binder.registerFormatter("myFieldName", new MyCustomFieldFormatter());
  }        
  ...
}

This is exactly what I want, but this a preview document from 2009 and it doesn't look like the registerFormatter method made it into the final released API.

How are you supposed to do this?

Answer 1

In our application, we use PropertyEditorSupport class for this. Simple example for handling Calendar, but you can use for any custom class, just override getAsText() and setAsText() methods:

@InitBinder
public void initBinder(WebDataBinder binder) {
    binder.registerCustomEditor(Calendar.class, new PropertyEditorSupport() {
        @Override
        public void setAsText(String value) {
            try {
                Calendar cal = Calendar.getInstance();
                cal.setTime(new SimpleDateFormat("dd-MM-yyyy").parse(value));
                setValue(cal);
            } catch (ParseException e) {
                setValue(null);
            }
        }

        @Override
        public String getAsText() {
            if (getValue() == null) {
                return "";
            }
            return new SimpleDateFormat("dd-MM-yyyy").format(((Calendar) getValue()).getTime());
        }
    });
}