Duplicate JSON Field with Jackson

Question

I am using Jackson for JSON (de)serialization in conjunction with Spring. However I am having an issue with a field being twice in some cases.

I have an abstract cla

Answer 1

This behaviour is caused by the annotations placed on class AbstractBookmarkJsonModel:

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "mimeType")
@JsonSubTypes({
    @JsonSubTypes.Type(value = ImageBookmarkJsonModel.class, name = "image/jpeg"),
    @JsonSubTypes.Type(value = EpubBookmarkJsonModel.class, name = "application/epub+zip")
})

@JsonTypeInfo tells Jackson to serialize the logical type name (JsonTypeInfo.Id.NAME) as a property (JsonTypeInfo.As.PROPERTY) with name mimeType (property = "mimeType"). With @JsonSubTypes.Type you assign the logical name application/epub+zip to EpubBookmarkJsonModel.

When it comes to serialization, Jackson serializes the logical name as a property mimeType = "application/epub+zip" then the properties of the object among them mimeType which happens to have the same value as the logical name application/epub+zip (assigned in the constructor).

I think mimeType should be changed to objectType in the @JsonTypeInfo annotation or even better to remove the mimeType field since Jackson will take care of that through type info serialization.