Spring Boot：为什么自定义验证器类中的自动连线对象为空？

Question

以下代码在isValid（）函数内的teamResource自动连线对象上生成null：

@Component //I am not sure it is required he
public class TeamIdValidator implements ConstraintValidator<TeamIdConstraint, Integer> {
    
    @Autowired private TeamResource teamResource;
    
    public TeamIdValidator() {
    }

    @Override
    public void initialize(TeamIdConstraint teamIdConstraint) {
        // this.teamIdConstraint = teamIdConstraint;
    }

    @Override
    public boolean isValid(Integer teamId, ConstraintValidatorContext cxt) {

        int numOfAvailableTeams = teamResource.retrieveAllTeams().size(); //teamResource is null :(

        return teamId < 0 || teamId >= numOfAvailableTeams;
    }
}

团队资源类：

@RestController
@CrossOrigin
public class TeamResource {
    
    @Autowired private TeamRepository teamRepository;
    
    public TeamResource() {
    }
    ...

   //mapping methods
}

如果相关的话。。。

@Documented
@Constraint(validatedBy = TeamIdValidator.class)
@Target({ ElementType.METHOD, ElementType.FIELD, ElementType.PARAMETER })
@Retention(RetentionPolicy.RUNTIME)
public @interface TeamIdConstraint {
    
    String message() default "Invalid team id!";

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

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

到底为什么teamResources是null？

它没有在任何其他地方用new显式初始化。

Answer 1

已经在评论中提到了，但是声明一个像这样的bean

@Configuration
public class ValidationConfig{

    @Bean
    public LocalValidatorFactoryBean validator() {
        return new LocalValidatorFactoryBean();
    }

    @Bean
    public MethodValidationPostProcessor methodValidationPostProcessor(Validator validator) {
        MethodValidationPostProcessor methodValidationPostProcessor = new MethodValidationPostProcessor();
        methodValidationPostProcessor.setValidator(validator);
        return methodValidationPostProcessor;
    }

}

移除所有@autowired、prefere构造函数注入。（上网查看原因）。

然后，向验证器注入RestContoller是没有意义的。