Unable to use Bean Validation with JSON-B in RESTEasy 3.x

Original jira: RESTEASY-2107

When trying to use the JSON-B provider (aka json-binding) with a BV related example, I discovered it does not play well with the Bean Validation support:

Caused by: org.jboss.resteasy.core.NoMessageBodyWriterFoundFailure: Could not find MessageBodyWriter for response object of type: org.jboss.resteasy.api.validation.ViolationReport of media type: application/json
at org.jboss.resteasy.core.ServerResponseWriter.lambda$writeNomapResponse$2(ServerResponseWriter.java:105)
at org.jboss.resteasy.core.interception.jaxrs.ContainerResponseContextImpl.filter(ContainerResponseContextImpl.java:405)
at org.jboss.resteasy.core.ServerResponseWriter.executeFilters(ServerResponseWriter.java:218)

The issue here is that ViolationReport has some JAXB annotations (as we also need it to work with XML) and, in this case, the JSON-B provider is not considered as valid:
https://github.com/resteasy/Resteasy/blob/3.6/providers/json-binding/src/main/java/org/jboss/resteasy/plugins/providers/jsonb/JsonBindingProvider.java#L68

I don't think these JAXB conditions is a good idea for 2 reasons:

• having JAXB annotations don't say you won't use JSON to serialize the object;
• JAXB is gone in stock JDK 11 and the JsonBindingProvider won't work if JAXB is not in the classpath. So you would need to add a JAXB API jar to your classpath to have JSON-B working, which sounds like a bad idea.

I think we should get rid of these JAXB conditions (and of the condition on the presence of JSON-B annotations as they are not required and it won't make sense anymore).

Example:
Server side:

@Path("/")
public class ValidationResourceWithReturnValues {
    @POST
    @Path("/post")
    @Produces("application/json")
    public String post(@Size(min = 5, max = 10) String s) {
        return s;
    }
}

Client side:

public class App {
    static Client client;
    public static void main(String[] args) throws Exception {
        client = ClientBuilder.newClient();
        WebTarget target = client.target("http://localhost:8080/jaxrs-wf/post");
        Response response = target.request().accept(MediaType.APPLICATION_JSON).post(Entity.text("aa"));
        ViolationReport r = response.readEntity(ViolationReport.class);
        System.out.println(r.toString());
        System.out.println(r.getParameterViolations().get(0).getValue());
    }
}

        <dependency>
            <groupId>org.jboss.resteasy</groupId>
            <artifactId>resteasy-client</artifactId>
            <version>${version.resteasy}</version>
        </dependency>
        <!--<dependency>-->
            <!--<groupId>org.jboss.resteasy</groupId>-->
            <!--<artifactId>resteasy-jackson2-provider</artifactId>-->
            <!--<version>${version.resteasy}</version>-->
        <!--</dependency>-->
        <dependency>
            <groupId>org.jboss.resteasy</groupId>
            <artifactId>resteasy-json-binding-provider</artifactId>
            <version>${version.resteasy}</version>
        </dependency>