Thanks for the feedback. Just to loop back - I ended up bypassing Mixins
and customizing my ObjectMapper to seek out the inner Builder class via
reflection.
@Slf4j
public class CustomObjectMapper extends ObjectMapper{
private static final long serialVersionUID = 1L;
public CustomObjectMapper() {
this.setAnnotationIntrospector(new JacksonAnnotationIntrospector() {
private static final long serialVersionUID = 1L;
@Override
public Class<?> findPOJOBuilder(AnnotatedClass ac) {
//log.info(Class.forName(ac.getName()+"$"+ac.getRawType().getSimpleName()+"Builder");
Class<?> innerBuilder;
try {
innerBuilder = Class.forName(ac.getName()+"$"+ac.
getRawType().getSimpleName()+"Builder");
log.info("Builder found: {}", ac.getName());
return innerBuilder;
} catch( ClassNotFoundException e ) {
return super.findPOJOBuilder(ac);
}
}
@Override
public Value findPOJOBuilderConfig(AnnotatedClass ac) {
if (ac.hasAnnotation(JsonPOJOBuilder.class)) {
return super.findPOJOBuilderConfig(ac);
}
return new JsonPOJOBuilder.Value("build", "");
}
});
}
}
On Thursday, January 24, 2019 at 8:45:02 PM UTC-8, Tatu Saloranta wrote:
>
> On Thu, Jan 24, 2019 at 8:39 PM pscl <[email protected] <javascript:>>
> wrote:
> >
> > Hi,
> >
> > Here's a question I've posted on SO - crossposting here in hope of
> getting some domain-expertise.
> >
> >
> > I have a 3rd party Lombok builder POJO, one that I cannot modify, that I
> want to serialize using jackson. Notably it does not have a
> NoArgsConstructor.
> >
> > @Data
> > @Builder
> > public class ExternalClass {
> > private String name;
> > private String data;
> > // etc.
> > }
> >
> >
> > On the surface this would appear to be simple, but it is incredibly
> frustrating in practice as each possible option seems to be counteracted by
> a different complication. In essence, I'm having trouble getting an
> external Lombok builder to work with a jackson mixin.
> >
> >
> > Lombok produces fluent setters of the style .name(String name) while
> Jackson's built-in builder deserializer expects .withName(String name).
> Lombok documentation, and recipes elsewhere such as here suggest using
> @JsonDeserialize(builder=ExternalClass.ExternalClassBuilder.class) in
> conjunction with @JsonPOJOBuilder(withPrefix="") on a predeclared inner
> stub builder. But this is not possible because the Lombok class is in an
> external library.
> >
> > Applying these annotations to a mixin has no effect.
>
> As explained, that approach should work, I think, as long as mixins
> are bound to targets properly (that is, value class mixin has
> annotation pointing to target class; builder class mixin has overrides
> for prefix name).
> So I may be missing something here, but what? Is builder class not
> available from sources and only materialized as part Lombok
> processing?
>
> > @JsonDeserialize(ExternalClass.ExternalClassBuilder.class)
> > public abstract class ExternalClassMixin {
> > @JsonPOJOBuilder(withPrefix="")
> > public static ExternalClassBuilder {
> > }
> > }
> >
> >
> > The only approach I've found that works is to leverage the
> package-access AllArgsConstructor created by @Builder and populate the
> mixin with the following constructor
>
> Note that as long as annotation exists, AllArgsConstructor can even be
> private, if that matters; Jackson can access it via reflection (unless
> Java 11+ start blocking that or something).
>
> >
> > public abstract class ExternalClassMixin {
> > @JsonCreator public ExternalClassMixin(
> > @JsonProperty("name") String name,
> > @JsonProperty("data") String data,
> > // etc.
> > ) {}
> > }
> >
> >
> > This is obviously not desirable as it requires iterating and hard-coding
> every class property explicitly, making the mixin fragile to any change in
> the external POJO.
> >
> > My question is - is there a robust, maintainable way to serialize this
> external builder class using Jackson without modifying it, using either a
> mixin or maybe a full blown deserializer?
>
> If mixin-for-builder approach does not, maybe others have ideas.
>
> One interesting thing to note is that Jackson can actually override
> settings on final properties too.
> So as long as there are public accessors, these would be found.
>
> -+ Tatu +-
>
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