mike-neck / data-utilities

Basic data utilities for Java 8 or later.

Data utilities

This libraries offers data types representing some common logic.

Usages

For example, UserRepository interface is given with signature like bellow and you are going to implement user login feature in UserService.

interface UserRepository {
  @NotNull
  Optional<User> findUserByEmail(@NotNull String email);
}

interface UserService {
  @NotNull
  UserName login(@NotNull String email, @NotNull String password);
}

In the normal case this service will be implemented as follows.

class UserServiceImpl {
  private final UserRepository repository;
  private final HashService hashService;

  @Override
  @NotNull
  public Username login(@NotNull String email, @NotNull String password) {
    final Optional<User> user = repository.findUserByEmail(email);
    if (!user.isPresent()) {
      throw new UserNotFoundException("Invalid email and password.");
    }
    final User u = user.get();
    if (hashService.validateHash(u.getPasswordHash(), password)) {
      return u.getName();
    } else {
      throw new UserNotFoundException("Invalid email and password.");
    }
  }
}

With this library you can implement this method with method chain.

class UserServiceImpl {
  private final UserRepository repository;
  private final HashService hashService;

  @Override
  @NotNull
  public Username login(@NotNull String email, @NotNull String password) {
    return repository.findUserByEmail(email)
        .map(Tuple.mkTuple(User::getPasswordHash)) // User -> Tuple<User, PasswordHash>
        .filter(Tuple.conditionTuple(hash -> hashService.validateHash(hash, password)))
        .map(Tuple::getLeft) // Tuple<User, String> -> User
        .orElseThrow(() -> new UserNotFoundException("Invalid email and password."));
  }
}