无法使用spring数据仓库中的deleteBy自定义方法执行删除操作

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String username;
    // getters and setters
}

import org.springframework.data.jpa.repository.JpaRepository;

public interface UserRepository extends JpaRepository<User, Long> {
    void deleteByUsername(String username);
}

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

@Service
public class UserService {

    @Autowired
    private UserRepository userRepository;

    @Transactional
    public void deleteUserByUsername(String username) {
        userRepository.deleteByUsername(username);
    }
}