How to use Java 8 Optional properly that can conditionally return a value or throw exception?

Question

I want to implement something like below code to validate inputs in my @RestController so that I can avoid explicit null checks, However I am stuck.

public @ResponseBody Response getCityDetails(@RequestParam("city") final String city) {
    Optional.of(city).ifPresent(name -> {
        // return value
        return service.getDetails(name);
    }).orElseThrow(//some Exception);
}

Answer 1

Try this

Optional.ofNullable(city)
        .map(name ->service.getDetails(name))
        .orElseThrow(//some Exception);