Presenter in Clean Architecture

presenter.kt

// shared datastructures

data class ResponseModel(val value: String)
data class JsonResponse(val jsonValue: String)

// example 1

interface FooUseCase { 
   fun <T> T doSomething(presenter: (ResponseModel -> T))
}

@RestController
@RequestMapping("/bar")
class Controller(val useCase: FooUseCase) {
   @GetMapping
   fun bar() : JsonResponse {
     return useCase.doSomething { responseModel ->  JsonResponse(responseModel.value) }
   }
}

// example 2

interface FooUseCase { 
   fun doSomething(presenter: Consumer<ResponseModel>)
}

class JsonPresenter() : Consumer<ResponseModel> {
  private var presented : JsonResponse
  
  fun accept(responseModel responseModel) {
     presented = JsonResponse(responseModel.value)
  }
  
  fun getPresentedState() = presented
}

@RestController
@RequestMapping("/bar")
class Controller(val useCase: FooUseCase) {
   @GetMapping
   fun bar() : JsonResponse {
     val presenter = JsonPresenter()
     useCase.doSomething(presenter)
     return presenter.getPresentedState();
   }
}

// example 3

interface FooUseCase { 
   fun doSomething(presenter: Consumer<ResponseModel>)
}

class JsonPresenter(val httpResponse: HttpServletResponse) : Consumer<ResponseModel> {
  fun accept(responseModel: ResponseModel) {
     httpResponse.getWriter().println(ObjectMapper().writeAsString(responseModel))
  }
}

@RestController
@RequestMapping("/bar")
class Controller(val useCase: FooUseCase) {
   @GetMapping
   fun bar(val httpResponse: HttpResponse) {
     val presenter = JsonPresenter(httpResponse)
     useCase.doSomething(presenter)
   }
}