Spring Boot JPA CrudRepository如何设置可选的搜索参数

import org.springframework.data.repository.CrudRepository;

public interface UserRepository extends CrudRepository<User, Long> {
}

import org.springframework.data.repository.CrudRepository;

public interface UserRepository extends CrudRepository<User, Long> {
    List<User> findByFirstNameAndLastName(String firstName, String lastName);
}

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class UserService {
    private final UserRepository userRepository;

    @Autowired
    public UserService(UserRepository userRepository) {
        this.userRepository = userRepository;
    }

    public List<User> searchUsers(String firstName, String lastName) {
        if (firstName != null && lastName != null) {
            return userRepository.findByFirstNameAndLastName(firstName, lastName);
        } else if (firstName != null) {
            return userRepository.findByFirstName(firstName);
        } else if (lastName != null) {
            return userRepository.findByLastName(lastName);
        } else {
            return userRepository.findAll();
        }
    }
}