如何为`javax.validation.constraints`注解添加自定义验证器？

import javax.validation.Constraint;
import javax.validation.Payload;
import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;
import java.lang.annotation.*;

@Target({ElementType.FIELD, ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = CustomValidator.class)
public @interface CustomValidation {

    String message() default "Invalid value";

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

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

public class CustomValidator implements ConstraintValidator<CustomValidation, String> {

    @Override
    public void initialize(CustomValidation constraintAnnotation) {
        // 初始化操作
    }

    @Override
    public boolean isValid(String value, ConstraintValidatorContext context) {
        // 自定义验证逻辑，返回验证结果
        return value != null && value.matches("\\d+");
    }
}

public class MyClass {

    @CustomValidation(message = "Invalid age")
    private String age;

    public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }
}

public class Main {

    public static void main(String[] args) {
        MyClass obj = new MyClass();
        obj.setAge("18");

        ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
        Validator validator = factory.getValidator();
        Set<ConstraintViolation<MyClass>> violations = validator.validate(obj);

        for (ConstraintViolation<MyClass> violation : violations) {
            System.out.println(violation.getMessage());
        }
    }
}