如何使用 Jackson AnnotationIntrospector 有条件地忽略属性

问题描述

我想创建一个注释，让 Jackson 忽略带注释的字段，除非设置了某个跟踪级别:

I want to create an annotation to make Jackson ignore the annotated fields unless a certain tracing level is set:

public class A {
    @IgnoreLevel("Debug") String str1;
    @IgnoreLevel("Info") String str2;
}

或者，如果这更容易实现，我也可以为不同级别分别添加注释:

Or, if this is easier to implement, I could also have separate annotations for the different levels:

public class A {
    @Debug String str1;
    @Info String str2;
}

根据ObjectMapper的配置，要么

• 在序列化和反序列化时应忽略所有调试"和信息"字段，或
• 应忽略所有调试"字段，或
• 所有字段都应序列化/反序列化.

我想这应该可以通过自定义 AnnotationIntrospector.我有这个 post，但它没有展示如何实现自定义 AnnotationIntrospector 的示例.

I suppose that this should be possible with a custom AnnotationIntrospector. I have this post, but it doesn't show an example of how to implement a custom AnnotationIntrospector.

推荐答案

如果你想对 JacksonAnnotationIntrospector 进行子类化，你只需要覆盖 hasIgnoreMarker，比如:

If you want to sub-class JacksonAnnotationIntrospector, you just need to override hasIgnoreMarker, something like:

@Override
public boolean hasIgnoreMarker(AnnotatedMember m) {
  IgnoreLevel lvl = m.findAnnotation(IgnoreLevel.class);
  // use whatever logic necessary
  if (level.value().equals("Debug")) return true;
  return super.hasIgnoreMarker();
}

但请注意，每个类只进行一次注解内省，因此您无法动态更改您使用的标准.

but note that annotation introspection only occurs once per class so you can not dynamically change the criteria you use.

对于更多的动态过滤，您可能希望使用 JSON 过滤器功能，例如:http://www.cowtowncoder.com/blog/archives/2011/09/entry_461.html

For more dynamic filtering you may want to rather use JSON Filter functionality, see for example: http://www.cowtowncoder.com/blog/archives/2011/09/entry_461.html

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