combination of result and single/multi for spring webflux

[astmuc]

Is there a way to achieve result types like

Mono<ResponseEntity<SomeBean>>

instead of

ResponseEntity<Mono<SomeBean>> 

I need to set header properties in the response (e.g. Etag) which depend on the result processing (SomeBean).
Currently i use this mapping.yaml snippet

map:
  result: org.springframework.http.ResponseEntity

  single: reactor.core.publisher.Mono
  multi: reactor.core.publisher.Flux

[hauner]

I understand that this will not work because the eTag() depends on the result of SomeBean:

return ResponseEntity.ok ()
     .eTag("foo")
     .body (result of SomeBean);

which is a ResponseEntity<Mono<SomeBean>>

and you would like to do something like this:

return someBean.getResult()
       .map(r -> ResponseEntity.ok()
       .eTag(r.getEtag())
       .body(r));

which is a Mono<ResponseEntity<SomeBean>>

There is currently no official feature to switch the order of Mono/ResponseEntity.

Anyway, there are two workarounds

Object workaround

  paths:
    /some-bean-endpoint:
      get:
        types:
          - type: SomeBean => java.lang.Object
        result: plain

this uses official features and will produce a Mono<Object> result. result: plain removes the ResponseEntity and the type mapping maps the result to Object.

You can now return Mono<ResponseEntity<SomeBean>> (or anything else) from the controller.

Works but loses the type information. Which may not be a problem because, usually we do not call the controller from code.

single/result workaround

it is possible to switch the target classes of single and result. This is not a wanted feature so I consider this a bit dirty...

map:
  paths:
    /some-bean-endpoint:
        single: org.springframework.http.ResponseEntity
        result: reactor.core.publisher.Mono

it is possible to minimize the effect to a specific http method

map:
  paths:
    /some-bean-endpoint:
      get: # http method
        single: org.springframework.http.ResponseEntity
        result: reactor.core.publisher.Mono

disabling single/result:

this does not apply to this case but it may help with other edge cases.

one can disable the single and result wrappers for an endpoint by setting one (or both) to plain:

  paths:
    /some-bean-endpoint:
        single: plain
        result: plain

[astmuc]

Thank you for the fast answer ! I will try the object workaround.