JAVA手写通过注解验证范围合规的值

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface IsNull {
    String Message();
}

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface NumRange {
    int Min();
    int Max();
    String Message();
}

public class MyValidationUtil {
    private static <T> List<String> Validate(T obj){
        ArrayList<String> warning = new ArrayList<>();
        Class clazz = obj.getClass();
        //获取类的所有属性
        Field[] declaredFields = obj.getClass().getDeclaredFields();
        for (Field declaredField : declaredFields) {
            //获取属性 declaredField.getName() 属性名
            Field field = null;
            try {
                field = clazz.getDeclaredField(declaredField.getName());
                field.setAccessible(true);
                Annotation[] annotations = field.getAnnotations();
                for (Annotation annotation : annotations) {
                    if (annotation instanceof IsNull) {
                        Object o = field.get(obj);
                        IsNull isNull = (IsNull) annotation;
                        if (o == null) {
                            warning.add(isNull.Message());
                        }
                    }
                    if (annotation instanceof NumRange) {
                        Object o = field.get(obj);
                        if (o instanceof Integer) {
                            int value = (Integer) o;
                            NumRange numRange = (NumRange) annotation;
                            //获取注解的属性值
                            if (!(value < numRange.Max() && value > numRange.Min())) {
                                warning.add("错误" + numRange.Message());
                            }
                        }
                    }
                }
            } catch (NoSuchFieldException | IllegalAccessException ignored) {
            }

        }
        return warning;
    }
}

    @NumRange(Min = 2,Max=99,Message="vipid为9-99")
    private Integer vipId;
    @IsNull(Message = "sex不能空")
    private Integer sex;
    @IsNull(Message = "名字不能空")
    private String vipName;