Return Either (Vavr) in rest api

Question

I have method:

@GetMapping
public Either<ResponseEntity<TaskError>,ResponseEntity<List<TaskDto>>> readAllOrderedByStatus() {

    var result = taskCrudService.readAllOrderedByStatus();

    if (result.isLeft()) {

        return Either.left(
                new ResponseEntity<>(
                        TaskError.TASKS_LIST_NOT_FOUND,
                        HttpStatus.NOT_FOUND));
    }

    return Either.right(new ResponseEntity<>(result.get(),HttpStatus.OK));
}

I want to return List and HTTP status or TaskError.TASKS_LIST_NOT_FOUND and HTTP status, but due to Either there are also additional things in Json like "right" etc.

Solution (thanks @chrylis -cautiouslyoptimistic)

@GetMapping
public ResponseEntity<?> readAllOrderedByStatus() {

    var result = taskCrudService.readAllOrderedByStatus();

    return taskCrudService
             .readAllOrderedByStatus()
             .fold(
                     error -> new ResponseEntity<>(error,HttpStatus.NOT_FOUND),
                     list -> new ResponseEntity<>(list,HttpStatus.OK));
}

score 3 · Accepted Answer · answered Aug 04 '21 at 16:11

I'm using Either for exactly this kind of concept in a REST API. You will need to be responsible for converting your Either into a consistent response. In most cases, including yours, you're needing fold:

return taskCrudService.readAllOrderedByStatus() // -> Either
  .fold(
    __   -> ResponseEntity.notFound(TASKS_LIST_NOT_FOUND).build(),
    list -> ResponseEntity.ok(list)
  );

Return Either (Vavr) in rest api

1 Answers1