自定义 ConstraintValidator 不工作（异常）

Question

我对 Spring 有疑问，尤其是 ConstraintValidator。我想为包含电子邮件的字段发布自定义验证。它必须是独一无二的。好的。任务很明确，我是这样做的：

UniqueEmail.java

@Constraint(validatedBy = UniqueEmailValidator.class)
@Target( { ElementType.METHOD, ElementType.FIELD })
@Retention(RetentionPolicy.RUNTIME)
public @interface UniqueEmail {
    String message() default "Invalid phone number";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
}

UniqueEmailValidator.java

public class UniqueEmailValidator implements ConstraintValidator<UniqueEmail, String> {

    private final UserRepository userRepository;

    public UniqueEmailValidator(UserRepository userRepository) {
        this.userRepository = userRepository;
    }

    @Override
    public boolean isValid(String email, ConstraintValidatorContext context) {
        return email != null && !userRepository.findByEmail(email).isPresent();
    }
}

User.java

@Data
@Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(unique = true)
    @NotEmpty(message = "Email should not be empty")
    @Email(message = "Email should be valid")
    @UniqueEmail(message = "Email address is already registered")
    private String email;

    @NotEmpty(message = "Password should not be empty")
    private String password;

    @NotEmpty(message = "Name should not be empty")
    @Size(min = 2, max = 30, message = "Name should be between 2 and 30 characters")
    private String username;

    private boolean enabled = true;

    @Enumerated(value = EnumType.STRING)
    private Role role;
}

UserRepository.java

public interface UserRepository extends JpaRepository<User, Long> {
    Optional<User> findByEmail(String email);
}

AuthController.java

@Controller
@RequestMapping("/auth")
public class AuthController {

    private final UserRepository userRepository;

    private final PasswordEncoder passwordEncoder;

    @Autowired
    public AuthController(UserRepository userRepository, PasswordEncoder passwordEncoder) {
        this.userRepository = userRepository;
        this.passwordEncoder = passwordEncoder;
    }

    @GetMapping("/login")
    public String login(Principal principal) {
        if(principal != null)
            return "redirect:/";
        return "auth/login";
    }

    @GetMapping("/register")
    public String register(@ModelAttribute("user") User user, Principal principal) {
        if(principal != null)
            return "redirect:/";
        return "auth/register";
    }

    @PostMapping("/register")
    public String newCustomer(Principal principal, Model model, @ModelAttribute("user") @Valid User user, BindingResult bindingResult) {
        if(principal != null)
            return "redirect:/";

        if(bindingResult.hasErrors())
            return "auth/register";

        user.setPassword(passwordEncoder.encode(user.getPassword()));
        user.setRole(Role.CUSTOMER);
        userRepository.saveAndFlush(user);

        model.addAttribute("success", true);
        model.addAttribute("user", new User());

        return "auth/register";
    }
}

如果我尝试输入现有的电子邮件，一切正常（收到消息“电子邮件地址已注册”）。但是，如果我尝试输入一封新电子邮件，我会收到错误消息“Servlet.service() for servlet [dispatcherServlet] in context with path [] throw exception [Request processing failed; nested exception is javax.validation.ValidationException: HV000064:无法实例化 ConstraintValidator：bla.bla.bla.validator.UniqueEmailValidator.] 具有根本原因。

我正在尝试使用@Component 和@Autowired，但得到了相同的结果。我正在尝试使用 noArgs 构造函数并得到 NullPointerException（未注入 UserRepository）。

为什么？没看懂。

Answer 1

上述错误是因为您的 UniqueEmailValidator 的构造函数为空。另见：javax.validation.ValidationException: HV000064: Unable to instantiate ConstraintValidator

您可以使用@Autowired 注释将 userRepository 注入您的约束验证器，如前所述：

此处：Inject Spring Beans into Annotation-based Bean Validator
这里：https://docs.spring.io/spring-framework/docs/current/reference/html/core.html#validation-beanvalidation-spring-constraints

另外请注意在所有相关的控制器方法User user之前加上@Valid注解

Answer 2

这样问题就解决了。我知道这是一个拐杖，但我还没有找到其他解决方案。

@Component
public class UniqueEmailValidator implements ConstraintValidator<UniqueEmail, String> {

    private UserRepository userRepository;

    public UniqueEmailValidator() {
    }

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

    @Override
    public boolean isValid(String email, ConstraintValidatorContext context) {
        if(userRepository == null)
            return true;
        return email != null && !userRepository.findByEmail(email).isPresent();
    }
}

添加了 noArgs 构造函数，并在 isValid 函数中添加了 ckeck if null userRepository。

自定义 ConstraintValidator 不工作（异常）

Custom ConstraintValidator not working (Exception)

java

spring-data-jpa

spring-validator

spring-boot