Optional parameters for Request Param is a bad practise?

Question

I'm using Optional parameters for my Rest controller, in my case to distinguish which method to call:

@GetMapping("/cars")
@ResponseBody
public List<CarsDTO> getAllCarsByCat(@RequestParam Optional<Integer> cat1,
                                     @RequestParam Optional<Integer> cat2) {
    if (cat1.isPresent() && cat2.isPresent())
        return carsService.getAllCarsByCat1AndCat2(cat1.get(), cat2.get());
    else if (cat1.isPresent())
        return carsService.getAllCarsByCat1(cat1.get());
    else if (cat2.isPresent())
        return carsService.getAllCarsByCat2(cat2.get());
    else
        return carsService.getAllCars();

}

Why does the highest voted response of the thread below propose that "Using Optional parameters causing conditional logic inside the methods is literally contra-productive."?

Why should Java 8's Optional not be used in arguments

I do exactly that and consider it as the most readable and straight forward solution. What is bad with this approach?

The answers to this question will be opinion based and this question can be closed. In my opinion, your code without *Optional* would be more readable / understandable if you had plain *Integer* types: all *if* expressions would be compact, but passing parameters to the *carService* would be even compacter than it is now, because *Optional.get()* would not be needed. In your case *Optional* wrappers are created, but I would neglect related memory and performance effects, which would be an additional contra argument for others. — mentallurg, Dec 25 '19 at 18:46

Ryuzaki L · Accepted Answer · 2020-02-07T15:33:38.650

The only concern using Optional as @RequestParam is performance and creating Optional wrapper using Optional.OfNullable and unwrapping using Optional.get() or checking using Optional.ifPresent(). As a functional perspective it always looks good using Optional but as a good programmer it is an unnecessary additional operations wrapping and unwrapping. In spring Optional is allowed in @RequestParam to declare param as optional

By default, method parameters that use this annotation are required, but you can specify that a method parameter is optional by setting the @RequestParam annotation’s required flag to false or by declaring the argument with an java.util.Optional wrapper.

So you can simply make those @RequestParam as optional using required==false and follow the same approach using if else, you can also use Objects.nonNull for more readability or you can also use defaultValue

@GetMapping("/cars")
@ResponseBody
 public List<CarsDTO> getAllCarsByCat(@RequestParam(name="cat1", required=false) Integer cat1,
                                 @RequestParam(name="cat2", required=false) Integer cat2) {
     if (cat1!=null && cat2!=null)
         return carsService.getAllCarsByCat1AndCat2(cat1, cat2);
     else if (cat1!=null)
         return carsService.getAllCarsByCat1(cat1);
     else if (cat2!=null)
         return carsService.getAllCarsByCat2(cat2);
     else
         return carsService.getAllCars();

  }

Optional parameters for Request Param is a bad practise?

1 Answers1