How to specify a custom content type per response in Rest DSL OpenAPI spec?

[Laurin Niemeyer]

Hi all,

I’m using Camel’s Rest DSL (with the servlet component) and generating an
OpenAPI specification via camel-openapi-java-starter

In one of my routes, I’d like to have *different content types for
different response codes* in the generated OpenAPI spec — specifically:

   -

   201 → application/json
   -

   400 → application/problem+json

Here’s a simplified version of my setup:

restConfiguration()
    .component("servlet")
    .bindingMode(RestBindingMode.json)
    .dataFormatProperty("contentTypeHeader", "false")
    .apiContextPath("/openapi");

And my route:

rest("/v1/public-announcements")
    .post()
        .id("create-public-announcement")
        .type(CreatePublicAnnouncementRequest.class)
        .responseMessage().code(201).message("Created")
            .responseModel(CreateIncidentResponse.class).endResponseMessage()
        .responseMessage().code(400).message("Bad Request")
            .responseModel(ZoneApiErrorMessage.class).endResponseMessage()
        .to("direct:createPublicAnnouncement");

This works fine at runtime — the HTTP responses have the correct
Content-Type headers —
but in the generated OpenAPI spec, both 201 and 400 responses are listed
with:

"content": {
  "application/json": { ... }}

Is there a way in the Rest DSL or via OpenAPI configuration to override the
response content type per response (e.g. make the 400 response use
application/problem+json)?

Thanks in advance for any pointers!
— Laurin Niemeyer