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我正在使用Sping Boot 进行个人项目。我收到以下错误：
未找到com.learningapp.backend.AcademixHub.services.UserService中构造函数的参数2需要类型为“com.learningapp.backend.AcademixHub.mappers.UserMapper”的Bean。
下面是UserService.java的代码：

@Service
public class UserService {
     private final UserRepository userRepository; 

        private final  PasswordEncoder passwordEncoder;

        private final UserMapper userMapper;    
        
        
    
    public UserService(UserRepository userRepository, PasswordEncoder passwordEncoder, UserMapper userMapper) {
            super();
            this.userRepository = userRepository;
            this.passwordEncoder = passwordEncoder;
            this.userMapper = userMapper;
        }

     public UserDto register(SignUpDto signupDto) {
         System.out.println("hello man hi hello");
            Optional<User> optionalUser = userRepository.findByEmail(signupDto.getEmail());

            if (optionalUser.isPresent()) {
                throw new AppException("Login already exists", HttpStatus.BAD_REQUEST);
            }

            User user = userMapper.signUpToUser(signupDto);
            user.setPassword(passwordEncoder.encode(signupDto.getPassword()));

            User savedUser = userRepository.save(user);

            return userMapper.toUserDto(savedUser);
        }
     
     public UserDto login(LoginDto loginDto) {
            User user = userRepository.findByEmail(loginDto.getEmail())
                    .orElseThrow(() -> new AppException("Unknown user", HttpStatus.NOT_FOUND));

            if (passwordEncoder.matches(loginDto.getPassword(), user.getPassword())) {
                return userMapper.toUserDto(user);
            }
            throw new AppException("Invalid password", HttpStatus.BAD_REQUEST);
        }

        public UserDto findByEmail(String login) {
            User user = userRepository.findByEmail(login)
                    .orElseThrow(() -> new AppException("Unknown user", HttpStatus.NOT_FOUND));
            return userMapper.toUserDto(user);
        }

}

字符串
下面是UserMapper.java的代码：

@Mapper(componentModel="spring")
@Component
public interface UserMapper {
    
    UserDto toUserDto(User user);
    
    @Mapping(target = "password", ignore = true)
    User signUpToUser(SignUpDto signUpDto);
    
}

型
如果我从这三个变量中删除final并添加一个默认构造函数，服务器可以正常运行。但是，如果我用POST请求命中register端点，我会得到另一个错误：
[请求处理失败：java.lang.NullPointerException：无法调用“com.learningapp.backend.AcademixHub.repository.UserRepository.findByEmail（String）”，因为“this.userRepository”为null]，根本原因是
我该怎么做才能解决这个问题？