ResponseBodyAdvice to accept null values? [SPR-12152]

[spring-projects-issues]

Ken Wang opened SPR-12152 and commented

ResponseBodyAdvice is amazing for my needs except for one thing, it doesn't seem to be triggered when the ResponseBody returns a null value.

Is it possible to handle this case through the ResponseBodyAdvice?

---

Affects: 4.1 GA

Issue Links:

• ResponseBodyAdvice to accept null values? [SPR-12153] #16767 ResponseBodyAdvice to accept null values? ("is duplicated by")
• Re-allow handling empty request body [SPR-12778] #17376 Re-allow handling empty request body

0 votes, 5 watchers

[spring-projects-issues]

Ken Wang commented

So I looked through the source code and found the deciding piece in the function RequestResponseBodyMethodProcessor.handleReturnValue(). In this function there is a null check that only runs AbstractMessageConverterMethodProcessor.writeWithMessageConverters() if returnValue is not null.

As far as I can tell by following the call chain, this returnValue is only required to be nonnull by the function AbstractMessageConverterMethodProcessor.writeWithMessageConverters() in which returnValue.getClass() is called.

However, if I understand it properly, this value can be obtained by returnType.getMethod().getReturnType().

So ideally, I'd like to get rid of this null check in RequestResponseBodyMethodProcessor.handleReturnValue(). Would this be a viable solution?

[spring-projects-issues]

Rossen Stoyanchev commented

I'll take a closer look, thanks.

[spring-projects-issues]

Ken Wang commented

Thanks man, much appreciated.

[spring-projects-issues]

Rossen Stoyanchev commented

I've added a fix. It turned out to be a little more complex since the return type could be ResponseEntity<?> in which case we've to obtain the generic parameter type.

[spring-projects-issues]

Ken Wang commented

Thank you for the fix! I hadn't thought about ResponseEntity, hope that wasn't too much of a hurdle.

[spring-projects-issues]

Rossen Stoyanchev commented

No worries. Thanks for the suggestion.