Example of Polymorphic Deserialization using Jackson

Polymorph.java

import com.fasterxml.jackson.annotation.JsonSubTypes;
import com.fasterxml.jackson.annotation.JsonTypeInfo;
import com.fasterxml.jackson.databind.PropertyNamingStrategy;
import com.fasterxml.jackson.databind.annotation.JsonNaming;


@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type")
@JsonSubTypes({
    @JsonSubTypes.Type(value=AudioAttachment.class, name="audio"),
    @JsonSubTypes.Type(value=LinkAttachment.class, name="link")
})
public class Attachment {

}

@JsonNaming(PropertyNamingStrategy.LowerCaseWithUnderscoresStrategy.class)
public class Audio {
    public int aid;
    public int ownerId;
}

public class AudioAttachment extends Attachment {
    public Audio audio;
}

public class Link {
    public String url;
    public String title;
}

public class LinkAttachment extends Attachment {
    public Link link;
}

Excellent tutorial!