How to set a prefix on validation messages

[kabadisha]

Hi,

I want to use the setPrefix(String prefix) method of DefaultMessageCodesResolver to set a different prefix when each of my different forms is being validated.

Where do I get the instance of DefaultMessageCodesResolver from?
I have tried getting it in my form handler like so:

protected void onBindAndValidate(HttpServletRequest request, Object command, BindException errors)
     		throws Exception {
    	DefaultMessageCodesResolver resolver = (DefaultMessageCodesResolver) this.getMessageCodesResolver();
    	resolver.setPrefix("editProduct.");
    }

But this throws a Null pointer exception (presumably because the MessageCodesResolver has not been instanciated at this point).

Any help would be greatly appreciated.
Thanks.