如何在Kotlin中列出字段注释? [英] How to list field annotations in Kotlin?

问题描述

我有一个注释

public @interface Field {
    String value();
}

和带有注释的java类:

and java class, annotated by it:

public class Animal {
    @Field("name")
    private String name;
}

我尝试通过下一个代码列出所有字段的注释:

I try to list all field' annotations by the next code:

for(field in clazz.declaredFields){
            for(annotation in field.annotations){
                when(annotation){
                     is Field -> {
                         //do something
                     }
                }
            }
        }

克拉兹是Class<T>

但field.annotations为空.

如何正确列出注释?

推荐答案

问题不是Kotlin特有的，您只是没有正确配置Field批注.默认情况下，每个注释都通过 RetentionPolicy.CLASS ，这意味着将无法通过反射对其进行访问.您必须使用 RetentionPolicy.RUNTIME 如果要在运行时中访问注释.

The issue isn't Kotlin specific, you just haven't configured Field annotation properly. By default, each annotation is retained with RetentionPolicy.CLASS, meaning it won't be accessible via reflection. You have to use RetentionPolicy.RUNTIME if you want to access the annotation in the runtime.

@Retention(RetentionPolicy.RUNTIME)
public @interface Field {
  String value();
}

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