使用Jackson Java反序列化派生类

Question

I have a base class as follows:

public class Criteria {
    private CriteriaType type;
        //getters & setters
        public enum CriteriaType {
        Condition, Medication
    }
}

and derived classes

public class ConditionCriteria extends Criteria {
    private String a;
        //getters & setters
}

public class MedicationCriteria extends Criteria {
    private String b;
        //getters & setters
}

and another class

public class CriteriaGroup {
    Criteria criteria;
        //getters & setters
}

I send a serialized JSON string of CriteriaGroup class to the server using Jackson for (de)serialialization. And the service on the server looks like:

@Consumes(MediaType.APPLICATION_JSON)
@Produces(MediaType.APPLICATION_JSON)
public Response createCriteriaGroup(CriteriaGroup criteriaGroup) {...

However, JAckson does not convert the deserialized JSON to one of the derived classes. How can I achieve this mapping according to the type field of Criteria class?

Thanks..

I get an exception like this when deserializing a JSON of ConditionCriteria:

SEVERE: The exception contained within MappableContainerException could not be mapped to a response, re-throwing to the HTTP container
org.codehaus.jackson.map.exc.UnrecognizedPropertyException: Unrecognized field "a" (Class Criteria), not marked as ignorable
 at [Source: org.eclipse.jetty.server.HttpInput@3c92218c; line: 1, column: 92] (through reference chain: CriteriaGroup["criteria"]->Criteria["a"])
        at org.codehaus.jackson.map.exc.UnrecognizedPropertyException.from(UnrecognizedPropertyException.java:53)
        at org.codehaus.jackson.map.deser.StdDeserializationContext.unknownFieldException(StdDeserializationContext.java:267)

....

Answer 1

You will need to add @JsonTypeInfo in Criteria to enable use of additional type information, to support polymorphic types. You should be able to find example of that (just google for "jackson JsonTypeInfo").