杰克逊动态改变JsonIgnore

Question

I have a class and there are variables inside it as well. Sometimes I want to ignore some fields and sometimes not when deserializing (maybe at serializing too). How can I do it at Jackson?

Answer 1

For serialization, " filtering properties " blog entry should help. Deserialization side has less support, since it is more common to want to filter out stuff that is written.

One possible approach is to sub-class JacksonAnnotationIntrospector , override method(s) that introspect ignorability of methods (and/or fields) to use whatever logic you want.

It might also help if you gave an example of practical application, ie what and why you are trying to prevent from being deserialized.

Answer 2

You might want to use JsonViews ( took it originally from http://wiki.fasterxml.com/JacksonJsonViews - broken now - web archive link: https://web.archive.org/web/20170831135842/http://wiki.fasterxml.com/JacksonJsonViews )

Quoting it:

First, defining views means declaring classes; you can reuse existing ones, or just create bogus classes -- they are just view identifiers with relationship information (child inherits view membership from parents):

 // View definitions:
  class Views {
            static class Public { }
            static class ExtendedPublic extends PublicView { }
            static class Internal extends ExtendedPublicView { }
  }

  public class Bean {
            // Name is public
            @JsonView(Views.Public.class) String name;
            // Address semi-public
            @JsonView(Views.ExtendPublic.class) Address address;
            // SSN only for internal usage
            @JsonView(Views.Internal.class) SocialSecNumber ssn;
  }

With such view definitions, serialization would be done like so:

 // short-cut:
  objectMapper.writeValueUsingView(out, beanInstance, ViewsPublic.class);

  // or fully exploded:
  objectMapper.getSerializationConfig().setSerializationView(Views.Public.class);
  // (note: can also pre-construct config object with 'mapper.copySerializationConfig'; reuse)
  objectMapper.writeValue(out, beanInstance); // will use active view set via Config

  // or, starting with 1.5, more convenient (ObjectWriter is reusable too)
  objectMapper.viewWriter(ViewsPublic.class).writeValue(out, beanInstance);
and result would only contain 'name', not 'address' or 'ssn'.

Answer 3

You should probably look at the modules feature of recent Jackson versions.

One possible mechanism would be to use a BeanDeserializerModifier .

I've been looking for a useful online tutorial or example, but nothing immediately appears. It might be possible to work something up if more is known of your context. Are you managing your ObjectMapper s manually, or using them in a JAX-RS setting, injected in Spring, or what?