WELD and HibernateValidator - ConstraintViolations always reported as "text/plain".

[chrisjr]

Hi,

I am running WELD 2.3.1.Final inside Tomcat 8, along with RESTeasy 3.0.13.Final and Hibernate Validator 5.1.3.Final, and I have discovered that constraint violations from Hibernate Validator are always being reported as MIME type "text/plain". My understanding of Hibernate Validator is that the ValidationReport is supposed to be returned as JSON if the HTTP Accept request header is set to "application/json".

I have created two example projects; one with WELD, RESTeasy and Hibernate Validator, and the other with just RESTeasy and Hibernate Validator. Only the project containing WELD has the buggy behaviour, which makes me suspect that there is a problem with the WELD + RESTeasy integration. (Both projects contain an Arquillian test that violates the same Hibernate Validator constraint).

Could I have missed something when adding Hibernate Validator to the project, please? I have added both the resteasy-cdi and hibernate-validator-cdi "bridging" artifacts to the WAR, and validation is happening... but I really would prefer the constraint violations to be reported as JSON. Upgrading to Hibernate Validator 5.2.2.Final makes no difference either.

There is also this log message:

2015-11-23 21:33:54,298 INFO localhost-startStop-1 i18n - RESTEASY008550: Unable to find CDI supporting ValidatorFactory. Using default ValidatorFactory

but I can't find any way of resolving this. (Having said that, it's not even considered to be warning).

Thanks for any assistance here; is this a bug please?

Cheers,

Chris

[mkouba]

Hi Chris,

I think this is more a question for RESTEasy team. When looking at the ResteasyViolationExceptionMapper it seems only "text/plain" is supported for ConstraintViolationException thrown by Hibernate Validator's ValidationInterceptor (used to validate CDI beans deployed as JAX-RS resources). JAX-RS spec also does not require any special handling here, see also 7.6 Validation and Error Reporting: "...the exact content and format of this entity is beyond the scope of this specification...".

[chrisjr]

Hi Martin,

When I examined the ResteasyViolationExceptionMapper, the problem appeared to be that ResteasyViolationException.getAccept() was always returning "text/plain" rather than the "application/json" which I was explicitly passing via the HTTP Accept header. So as I understand it, I think Resteasy should be executing this block of code:

// Check standard media types.
MediaType mediaType = getAcceptMediaType(exception.getAccept());
if (mediaType != null)
{
    builder.type(mediaType);
    builder.entity(new ViolationReport(exception));
    return builder.build();
}

where getAcceptMediaType(List<MediaType> accept) is where Resteasy implements the logic described in Chapter 51. Validation

I also think that any effort to convince the Resteasy developers that it was their problem would go something like this:

Resteasy: Does it work with just Resteasy and Hibernate Validator?
Me:          Yes, it does. (See resteasy-violator.tar)

Resteasy: Well, then...!

Cheers,

Chris

[mkouba]

The question is whether the exception mapper recieves an instance of ResteasyViolationException. For CDI beans it might be ConstraintViolationException so that it always returns MediaType.TEXT_PLAIN (see also the last line in toResponse() method).

WRT RESTEasy - first I'm not really sure it is implementable. And you probably cannot even force them to implement this as it's not required by the spec. However, I believe the team would be helpful if you ask them for help.

I wonder whether implementing a custom exception mapper would help...

[chrisjr]

Martin Kouba wrote:

And you probably cannot even force them to implement this as it's not required by the spec.

My point is that it is documented Resteasy behaviour rather than part of the JAX-RS specification:

If any constraint violations are detected, Resteasy will return a report in one of a variety of formats. If one of "application/xml" or "application/json" occur in the "Accept" request header, Resteasy will return an appropriately marshalled instance of org.jboss.resteasy.api.validation.ViolationReport

See Chapter 51. Validation. Basically, including WELD is breaking this behaviour somehow.

And yes, I have considered writing a custom exception mapper as a last resort.

[chrisjr]

Also raised as [RESTEASY-1264] RESTEasy + WELD + HibernateValidator - ConstraintViolations always reported as MIME "text/plain". - JBos…

[mkouba]

Thanks for info. I've added a comment.