Understanding Optional<T>.map()

Question

Reviewing an example use of Optional where the optional is first loaded with a database call and then mapped to a Spring security UserDetails instance. The code looks like this:

Optional<User> user = userRepository.findByName(username);
user.orElseThrow(()-> new UsernameNotFoundException("Ahhh Shuckkkks!!!");
return user.map(CustomUserDetails::new).get();

In the last line would that call equal return new CustomUserDetails(user.get()).

Also anyone know if there's an even shorter more fluid way to write the above example?

Answer 1

Yes, that would be equivalent. But the code should rather be written as

return userRepository.findByName(username)
    .map(CustomUserDetails::new)
    .orElseThrow(()-> new UsernameNotFoundException("Ahhh Shuckkkks!!!"));

That avoids a useless variable, isolates the exceptional case at the end, and avoids the nasty call to get(), which is only guaranteed to work fine here because you have called orElseThrow() before.