Spring Boot自定义验证器Service注入NPE问题及优化方案

import javax.validation.Constraint;
import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;
import javax.validation.Payload;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component; // 可以保留，但核心是嵌套类和LocalValidatorFactoryBean
import java.lang.annotation.*;

import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

/**
 * 确保电子邮件唯一性的自定义注解
 */
@Documented
@Target(FIELD)
@Retention(RUNTIME)
@Constraint(validatedBy = UniqueEmail.Validator.class) // 指定嵌套的Validator类
public @interface UniqueEmail {

    String message() default "该邮箱已被注册！"; // 默认错误消息

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};

    /**
     * 嵌套的UniqueEmailValidator实现
     */
    public class Validator implements ConstraintValidator<UniqueEmail, String> {

        @Autowired
        private UserService userService; // 确保UserService能够被注入

        @Override
        public void initialize(UniqueEmail constraintAnnotation) {
            // 可以进行初始化操作，例如获取注解的属性
        }

        @Override
        public boolean isValid(String email, ConstraintValidatorContext context) {
            // 如果email为空，交给@NotNull或@NotEmpty处理，这里只检查唯一性
            if (email == null || email.isEmpty()) {
                return true;
            }
            // 调用Service方法检查邮箱是否存在
            return !userService.findUserByUserEmail(email);
        }
    }
}

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.validation.beanvalidation.LocalValidatorFactoryBean;

/**
 * Bean Validation配置类
 */
@Configuration
public class ValidationConfiguration {

    @Bean
    @Primary // 标记为主ValidatorFactoryBean
    public LocalValidatorFactoryBean validator() {
        return new LocalValidatorFactoryBean();
    }
}

public boolean findUserByUserEmail(String email){
    if(userRepository.findByEmail(email)){ // 假设findByEmail返回User对象或Optional<User>
        return true;
    }
    return false;
}

public interface UserRepository extends JpaRepository<User,Long> {
   boolean findByEmail(String email); // 这个方法签名有问题，应该返回User或Optional<User>
}

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

public interface UserRepository extends JpaRepository<User, Long> {

   /**
    * 检查是否存在指定邮箱的用户
    * 推荐使用existsBy前缀的方法进行存在性检查
    * @param email 邮箱地址
    * @return 如果存在返回true，否则返回false
    */
   boolean existsByEmail(String email);

   // 如果还需要按用户名检查，也可以添加类似方法
   boolean existsByUsername(String username); // 假设User实体有username字段
}

import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
import org.springframework.security.crypto.password.PasswordEncoder;
import org.springframework.stereotype.Service;

@Service
public class UserService {

    private final UserRepository userRepository;
    private final PasswordEncoder passwordEncoder;

    public UserService(UserRepository userRepository) {
        this.userRepository = userRepository;
        this.passwordEncoder = new BCryptPasswordEncoder();
    }

    // ... 其他方法 ...

    /**
     * 检查用户邮箱是否存在
     * @param email 邮箱地址
     * @return 如果邮箱已存在，返回true；否则返回false
     */
    public boolean findUserByUserEmail(String email){
        // 直接调用existsByEmail方法，更高效
        return userRepository.existsByEmail(email);
    }
}

// ... UniqueEmail注解接口中的嵌套Validator类 ...
public class Validator implements ConstraintValidator<UniqueEmail, String> {

    @Autowired
    private UserService userService;

    @Override
    public void initialize(UniqueEmail constraintAnnotation) {}

    @Override
    public boolean isValid(String email, ConstraintValidatorContext context) {
        if (email == null || email.isEmpty()) {
            return true; // 如果为空，让@NotNull/@NotEmpty处理
        }
        // 使用优化后的Service方法进行存在性检查
        return !userService.findUserByUserEmail(email);
    }
}