Spring Controller fetch query parameter for a wrapper request class - spring

Question

I am trying to build RESTful web service by using spring 4.0
I have a controller:
#Controller
#RequestMapping("test")
public class Controller{
#RequestMapping("fetch",method=RequestMethod.GET)
#ResponseStatus(value=HttpStatus.OK)
#ResponseBody
public ResultResponse fetchController(ResultRequest req){
if((req.getName).equals("John"))
return new ResultResponse(100);
else
return new ResultResponse(0);
}
}
and my ResultRequest.class
public class ResultRequest{
private String name;
//getter,setter
}
If I hit the url to //host//contextPath/test/fetch?name=John
the controller will return the object ResultResponse(100)
my question is, there no #RequestParam or other annotation in the request parameter,
how does the spring controller know to set the query parameter "name" as the property of wrapper class
ResultRequest ?
Thanks

Answer 1

Spring uses implementations of an interface called HandlerMethodArgumentResolver for resolving arguments to pass to handler methods, ie. methods annotated with #RequestMapping.
One of these is a ModelAttributeMethodProcessor. Its javadoc states
Resolves method arguments annotated with #ModelAttribute and handles
return values from methods annotated with #ModelAttribute.
Model attributes are obtained from the model or if not found possibly
created with a default constructor if it is available. Once created,
the attributed is populated with request data via data binding and
also validation may be applied if the argument is annotated with
#javax.validation.Valid.
When this handler is created with annotationNotRequired=true, any
non-simple type argument and return value is regarded as a model
attribute with or without the presence of an #ModelAttribute.
Spring registers two objects of this type. One to handle parameters annotated with #ModelAttribute and one to handle ones without.
Further reading:
Form submit in Spring MVC 3 - explanation
An Errors/BindingResult argument is expected to be declared immediately after the model attribute, the #RequestBody or the #RequestPart arguments