java - Spring 启动 : Autowired fields are none

Question

我正在使用 java spring 创建一个电子日记应用程序，但我遇到了一个小问题。我决定创建具有状态模式的角色系统。所以这个系统的逻辑应该是这样的:

1. 在 Controller 中，接受请求后，创建上下文类的对象。上下文类的构造函数根据用户角色获得具体的RoleClass。(它使用工厂)
2. 在controller中我们调用我们想要执行的context的方法
3. 在上下文中我们调用我们想要执行的角色的方法。
4. 在角色类中我们调用我们想要执行的服务方法。

但是问题来了。当我启动程序时，所有 Autowiring 的服务领域都是空的。我给context类添加了@Service注解，但是没用。我还尝试为上下文类创建 bean，但没有任何改变。

这是我的程序在启动后打印的内容:

Caused by: java.lang.NullPointerException: Cannot invoke "com.diary.diary.service.UserService.getCurrentUser()" because "this.userService" is null

这是我的代码:

1. 这是我的UserController:

@RestController
@RequestMapping("/api/user")
public class UserController {

    @Autowired
    private UserService userService;

    @Autowired
    private UserContext userContext;

    @GetMapping("/marks")
    public ResponseEntity<Object> getMarks() {
        try {
            return ResponseEntity.ok(userContext.getMarks());
        } catch (Exception e) {
            return new ResponseEntity<>(e.getMessage(), HttpStatus.NOT_FOUND);
        }
    }
}

1. 这是我的 UserContext 类:

@Service
public class UserContext {
    private UserRole userRole;

    @Autowired
    private UserService userService;

    public UserContext() {
        userRole = RoleFactory.getUserRole(userService.getCurrentUser().getName());
    }

    public List<HomeworkGetModel> getHomework() throws UserNotFoundException {
        return userRole.getHomework();
    }

    public List<MarkGetModel> getMarks() throws UserNotFoundException {
        return userRole.getMarks();
    }
}

1. 这是我的 RoleFactory 类:

public class RoleFactory {
    private static UserRole userRole;

    public static UserRole getUserRole(String roleName) {
        if(userRole == null) {
            buildUserRole(roleName);
        }
        return userRole;
    }

    private static void buildUserRole(String roleString) {
        switch (roleString) {
            case RoleNames.DEFAULT -> userRole = new DefaultRole();
            case RoleNames.STUDENT -> userRole = new StudentRole();
            case RoleNames.TEACHER -> userRole = new TeacherRole();
            case RoleNames.ADMIN -> userRole = new AdminRole();
        }
    }
}

1. 角色的界面如下:

public interface UserRole {
    default UserGetModel getUser(long id) throws UserNotFoundException {
        throw new NotImplementedException();
    }

    default List<UserGetModel> getAllUsers() {
        throw new NotImplementedException();
    }

    default UserEntity updateUser(UserUpdateModel newUserData) throws UserNotFoundException {
        throw new NotImplementedException();
    }

    default UserEntity deleteUser() throws UserNotFoundException {
        throw new NotImplementedException();
    }

    default List<MarkGetModel> getMarks() throws UserNotFoundException {
        throw new NotImplementedException();
    }

    default List<MarkGetModel> getMarksByDate(String date) throws UserNotFoundException, ParseException {
        throw new NotImplementedException();
    }

    default List<MarkGetModel> getMarksBySubject(String subjectName) throws UserNotFoundException {
        throw new NotImplementedException();
    }

    default List<MarkGetModel> getMarksByDateAndSubject(DateAndSubjectModel dateAndSubject) throws UserNotFoundException, ParseException {
        throw new NotImplementedException();
    }

    default SubjectGetModel getSubject(long id) throws SubjectNotFoundException {
        throw new NotImplementedException();
    }

    default SubjectGetModel getSubject(String name) throws SubjectNotFoundException {
        throw new NotImplementedException();
    }

    default SchoolGetModel getSchoolById(long schoolId) throws SchoolNotFoundException {
        throw new NotImplementedException();
    }

    default SchoolGetModel getSchoolByNumber(int schoolNumber) throws SchoolNotFoundException {
        throw new NotImplementedException();
    }

    default List<SchoolGetModel> getSchools() {
        throw new NotImplementedException();
    }

    default ClassGetModel getSchoolClass(ClassGetByNumberModel classData) throws com.diary.diary.exception.school_class.ClassNotFoundException, SchoolNotFoundException {
        throw new NotImplementedException();
    }

    default List<ClassGetModel> getClasses() {
        throw new NotImplementedException();
    }

    default List<HomeworkGetModel> getHomework() throws UserNotFoundException {
        throw new NotImplementedException();
    }

    default List<HomeworkGetModel> getHomeworkByDate(String date) throws UserNotFoundException, ParseException {
        throw new NotImplementedException();
    }

    default List<HomeworkGetModel> getHomeworkBySubject(String subjectName) {
        throw new NotImplementedException();
    }

    default ClassEntity addClass(ClassAddModel classData) {
        throw new NotImplementedException();
    }

    default ClassEntity addUserToClass(AdminAddUserToClassModel userAndClassModel) {
        throw new NotImplementedException();
    }

    default ClassEntity deleteClass(long id) {
        throw new NotImplementedException();
    }

    default UserEntity removeUserFromClass(AdminRemoveUserFromClassModel userClassModel) {
        throw new NotImplementedException();
    }

    default SchoolEntity addSchool(SchoolAddModel schoolData) {
        throw new NotImplementedException();
    }

    default SchoolEntity deleteSchool(long id) {
        throw new NotImplementedException();
    }

    default UserEntity removeUserFromSchool(AdminRemoveUserFromSchoolModel userSchoolModel) {
        throw new NotImplementedException();
    }

    default SubjectEntity addSubject(SubjectAddModel subjectData) {
        throw new NotImplementedException();
    }

    default SubjectEntity updateSubject(SubjectUpdateModel newSubjectModel) {
        throw new NotImplementedException();
    }

    default SubjectEntity deleteSubject(SubjectDeleteModel subjectDeleteData) {
        throw new NotImplementedException();
    }

    default TimetableEntity addTimetable(TimetableAddModel timetableData) {
        throw new NotImplementedException();
    }

    default TimetableEntity updateTimetable(TimeTableUpdateModel newTimetableData) {
        throw new NotImplementedException();
    }

    default TimetableEntity deleteTimetable(long id) {
        throw new NotImplementedException();
    }

    default ClassEntity addTimetableToClass(TimetableClassModel timetableClass) {
        throw new NotImplementedException();
    }

    default ClassEntity deleteTimetableFromClass(long classId) {
        throw new NotImplementedException();
    }
}

1. 这是 UserService 类:

@Service @Configurable
public class UserService implements UserDetailsService {

    @Autowired
    private UserRepository userRepo;
    @Autowired
    private RoleRepository roleRepo;

    @Autowired
    private MarkMethods markMethods;

    private final BCryptPasswordEncoder bCryptPasswordEncoder
            = new BCryptPasswordEncoder();


    @Override
    public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
        UserEntity user = userRepo.findByLogin(username);
        if(user == null) {
            throw new UsernameNotFoundException("user with such login not found");
        }
        SimpleGrantedAuthority userRole = new SimpleGrantedAuthority(user.getRole().toString());
        return new User(Long.toString(user.getId()), user.getPassword(), List.of(userRole));
    }

    public List<MarkGetModel> getMarks() throws UserNotFoundException {
        checkUserRoleOrThrow(RoleNames.ADMIN, getCurrentUser());
        UserEntity student = getCurrentUser();
        return convertToMarkGetModelList(student.getMarks());
    }

那么可能是什么问题呢？如果您知道，请告诉我，我将不胜感激。

Answer 1

在这里使用构造函数 Autowiring :

public UserContext(@Autowire UserService userService) {
    this.userService = userService;
    userRole = RoleFactory.getUserRole(userService.getCurrentUser().getName());
}

我认为当 spring 使用私有(private)字段 Autowiring bean 时，它首先通过空构造函数创建对象，然后通过反射填充字段(这是有道理的)。但是您在空构造函数中执行了整个执行过程，因此此时该字段未 Autowiring 。