Orika - how to map inheritance and flattening? - orika

Question

I have been struggling with a task how to tell Orika to map an inherited structure that is flattened to DTO so that it may correctly resolve the implementation on reconstruction of an object. Here is an example of a simple structure with many nested objects:
abstract class Document {
// common values
}
class LegalDocument extends Document {
// complex object with many nested objects
}
class PersonalDocument extends Document {
// complex object with many nested objects
}
And let's say I have a reason to have an object flattened of the structure above:
class FlattenedDocument {
private String documentType = "LEGAL"; // "LEGAL" or "PERSONAL"
// flattened properties of Document and both its subclasses
}
I am able to tell Orika via CustomMapper<Document, FlattenedDocument> to map correctly the property documentType with a correct value based on an actual type (class) of the input document, but what I don't know how to do is the reverse situation. I need to tell Orika that when it converts from FlattenedDocument to one of the implementations of abstract Document, whether it should create the former or the latter by the value of documentType property. I can do that via CustomConverter or ObjectFactory but in both cases I am losing the benefit of byDefault().
Is there any way how to use the standard ClassMap with byDefault() option
factory.classMap(Document.class, FlattenedDocument.class).byDefault().register();
but with the possibility to tell Orika that it should re-instantiate the object based on the value of documentType field?
Thanks.

Answer 1

You can create a CustomConverter, that decides the type based on your field:
public class ShapeReverseConverter extends CustomConverter<ShapeDTO, Shape> {
#Override
public Shape convert(ShapeDTO source, Type<? extends Shape> destinationType, MappingContext mappingContext) {
if (Circle.class.getSimpleName().equals(source.type)) {
return mapperFacade.map(source, Circle.class);
} else {
return mapperFacade.map(source, Rectangle.class);
}
}
}
In Config you can map setting the type:
DefaultMapperFactory mapperFactory = new DefaultMapperFactory.Builder().build();
mapperFactory.classMap(Shape.class, ShapeDTO.class).byDefault()
.field("class.simpleName", "type")
.register();
mapperFactory.getConverterFactory().registerConverter(new ShapeReverseConverter());