HttpMessageNotReadableException responds with a 400 (not 415) [DATAREST-413]

Dave Syer opened DATAREST-413 and commented

This appears to be a regression (or maybe a new "feature") because older versions of SDR didn't have this problem. There are actually potentially a few problems:

1. SDR takes responsibility for rendering HttpMessageNotReadableException (instead of letting the user's app do it). That can be a courtesy because the default rendering in Spring MVC is horrid, but in a Spring Boot app it takes over from the default error rendering and ends up with less rich information for callers (you only get the exception message, no other information like path, status).

2. Normally Spring MVC sends 415, and that seems more appropriate, since it is content negotiation that failed, not syntax.

3. The body of the response is the HttpMessageNotReadableException and that can be problematic for serialization (since the "cause" is generally "this"). Jacskon seems to handle it fine, but GSON does not, and I'm sure there are other message converters that would fail on a cycle

Affects: 2.2.1 (Evans SR1)