如何获得泛型类型注释 [关闭]答案

【问题标题】：How can I get a generic type annotation [closed]如何获得泛型类型注释 [关闭]
【发布时间】：2021-05-13 08:00:20
【问题描述】：

请告诉我，如何获取泛型类型的注释？

示例：我有public List<@NotNull GuestForm> guests，我想获得 NotNull 注释。

public class BookingForm {
    public List<@NotNull GuestForm> guests;

    private List<String> amenities;

    private String propertyType;

    private Unrelated unrelated;

    public BookingForm(List<GuestForm> guests, List<String> amenities, String propertyType, Unrelated unrelated) {
        this.guests = guests;
        this.amenities = amenities;
        this.propertyType = propertyType;
        this.unrelated = unrelated;
    }
}

【问题讨论】：

你想要什么？你能说得清楚一点吗？
我想得到一个 List 中声明的所有注解的列表
这能回答你的问题吗？ Are annotations on a type parameter accessible in runtime?

标签： java reflection java-annotations

【解决方案1】：

public class BookingForm {
    public List<@NotNull GuestForm> guests;

    private List<String> amenities;

    private String propertyType;

    private Unrelated unrelated;

    public BookingForm(List<GuestForm> guests, List<String> amenities, String propertyType, Unrelated unrelated) {
        this.guests = guests;
        this.amenities = amenities;
        this.propertyType = propertyType;
        this.unrelated = unrelated;
    }
}

Object objectClass = requireNonNull(bookingForm); 
var fields = objectClass.getClass().getDeclaredFields(); // Object fields
var annotations = ((AnnotatedParameterizedType) fields [0].getAnnotatedType()).getAnnotatedActualTypeArguments()[0].getAnnotations(); // Annotations of Generic type in List

【讨论】：