`@JsonSerialize(contentAs=superType)` behavior disallowed in 2.7

[markwoon]

After updating to 2.7, I'm getting:

Failed to widen value type of [collection type; class java.util.SortedSet, contains [simple type, class org.pharmgkb.model.AccessionIdentifier]] with concrete-type annotation (value org.pharmgkb.model.BaseAccessionIdentifier), from 'getGenes': Class org.pharmgkb.model.BaseAccessionIdentifier not a super-type of [simple type, class org.pharmgkb.model.AccessionIdentifier]

The signature of the method in question is:

@JsonSerialize(contentAs = BaseAccessionIdentifier.class)
@JsonDeserialize(contentAs = BaseAccessionIdentifier.class)
public Set<AccessionIdentifier> getGenes() {
}

How am I suppose to annotate this to get it to work again?

[cowtowncoder]

Sounds like earlier versions did not verify that types are compatible. Assuming BaseAccessionIdentifier is a subtype of AccessionIdentifier, @JsonSerialize here would be problematic as it can really be guaranteed to match type; but I also don't think that should be necessary should it? Serialization annotations are only typically used to limit type to a supertype, and not to try to use specialized type. In that way @JsonSerialize and @JsonDeserialize behave in opposing ways; former to force more general type, latter for more specific.

[markwoon]

Our inheritance tree looks something like this:

• AccessionIdentifier (interface)
  • BaseAccessionIdentifier
    • ClassA
    • ClassB

I'm trying to limit what gets serialized here to only the properties defined in BaseAccessionIdentifier.

Do I need to define a custom serializer in this case?

[cowtowncoder]

@markwoon Hmmh. I can see that although such definition is not necessarily safe for all usage (since you could have alternative AccessionIdentifier implementations), it may be for some usage; and could just dynamically fail if so, instead of statically.

So perhaps this is a flaw after all.

[markwoon]

@cowtowncoder Does that mean that this is something that might change a future release?

And what would you recommend in the mean time?

[cowtowncoder]

@markwoon Right, I think I will try to fix this for 2.7.4.

In the meantime... good question. I am not sure if there is an easier way than custom serializer.
While forcing use of AccessionIdentifier would be easy (either by specifying that as content type, or marking typing as Static), getting this to use intermediate type is more difficult.

[cowtowncoder]

I was able to fix this, will be included in 2.7.4.

[markwoon]

@cowtowncoder Confirming this works for collections, but not for single objects.

This is failing:

@JsonSerialize(as = BaseAccessionIdentifier.class)
@JsonDeserialize(as = BaseAccessionIdentifier.class)
public AccessionIdentifier getReference() {
}

Error message:

com.fasterxml.jackson.databind.JsonMappingException: Failed to widen type [simple type, class org.pharmgkb.model.AccessionIdentifier] with annotation (value org.pharmgkb.model.BaseAccessionIdentifier), from 'getReference': Class org.pharmgkb.model.BaseAccessionIdentifier not a super-type of [simple type, class org.pharmgkb.model.AccessionIdentifier]

[cowtowncoder]

@markwoon could you file a new issue with that? Along with either reproduction, or at least type definitions needed. Stack trace would be helpful as well.