Dynamic polymorphic type handling with Jackson

Question

I have a class hierarchy similar to this one:

public static class BaseConfiguration {
}

public abstract class Base {
  private BaseConfiguration configurati         


        

Answer 1

Good answer provided by Programmer Bruce!

I have a case of polymorphism in which I want to keep the domain objects as POJOs and not use dependencies on Jackson annotations.

Therefore I preffer to use a custom deserializer and a Factory for decising the type or intantiating the concrete classes.

Here is my code ... (be aware that I have an Annotation Hierarchy which are in fact "User Tags" and not Java Annotations )

Here is the deserialization Method

public class AnnotationDeserializer extends StdDeserializer {

AnnotationDeserializer() {
    super(Annotation.class);
}

@Override
public Annotation deserialize(JsonParser jp, DeserializationContext ctxt)
        throws IOException, JsonProcessingException {

    ObjectMapper mapper = (ObjectMapper) jp.getCodec();
    ObjectNode root = (ObjectNode) mapper.readTree(jp);
    Class realClass = null;

    Iterator> elementsIterator = root.getFields();
    while (elementsIterator.hasNext()) {
        Entry element = elementsIterator.next();
        if ("type".equals(element.getKey())) {
            realClass = AnnotationObjectFactory.getInstance()
                    .getAnnotationClass(element.getKey());
            break;
        }
    }

    if (realClass == null)
        return null;
    return mapper.readValue(root, realClass);
}
}