Question

I have read the Spring documentation and I was not able to find relevant information regarding the expected behavior of a Spring MVC controller method returning null (with a return type of String).

Can someone please provide a reply or direct me to relevant documentation? Or to put it another way, what would be the benefit of returning null from a Spring MVC controller method?

Answer 1

In Spring 2, when you returned null from a controller you were saying to the Spring dispatcher that you don’t want it to search for a view.

You did this if you were handling the response yourself by writing the response content directly and then flushing the output stream (you were managing a file download for example).

If you didn’t return null, Spring would have forwarded to a view who would try to write to the response also, messing up your already written data or resulting in an exception if the response was already commited.

Returning null was a way of saying back off to Spring’s view resolver.

A lot of things changed in Spring 3 and now the same can be obtained by having an @RequestMapping annotated method that returns void.

If you have a return type of String but you return null I think that it uses the default RequestToViewNameTranslator for translating an incoming HttpServletRequest into a logical view name when the view name wasn’t explicitly supplied.