Deserializing enums as interfaces with Spring Data MongoDB [DATAMONGO-1884]

Joaquin Peñalver opened DATAMONGO-1884 and commented

I've currently a problem with serialize/deserialize process in MongoDB of an object that contains an attribute defined by a marker interface and the implementations of this interface are Enums.

My used versions are Spring Boot 1.5.2, Spring 4.3.7 and Spring-data-mongodb 1.10.1.

The piece of code afected is:

public interface EventType {
    String getName(); 
}

public interface DomainEvent extends Serializable {

    UUID getId();    
    LocalDateTime getOccurredOn();    
    EventType getEventType();    
    String getEventName();    
}

public abstract class AbstractDomainEvent implements DomainEvent {

    private UUID id;
    private LocalDateTime occurredOn;
    private EventType eventType;

    protected AbstractDomainEvent(EventType eventType) {
        this.id = UUID.randomUUID();
        this.occurredOn = LocalDateTime.now();
        this.eventType = eventType;
    }
}

public class MyEventOne extends AbstractDomainEvent {

    private Object myConcreteData;

    public MyEventOne(Object data) {

        super(MyEventType.EVENT_ONE);
        this.myConcreteData = data;
    }    
}

public enum MyEventType implements EventType {

    EVENT_ONE,
    EVENT_N;

    @Override
    public String getName() {
        return this.name();
    }    
}

Ok, well. My problem is when I try to deserialize an event persisted in mongoDB.

When I persist MyEventOne, Spring data mongo persist the object as:

{
    "_class" : "xxx.xxx.xxx.MyEventOne",
    "_id" : LUUID("d74478e7-258c-52c4-4fc5-aba20a30d4b6"),
    "occurredOn" : ISODate("2018-02-21T14:39:53.549Z"),
    "eventType" : "EVENT_ONE"
}

Note the eventType is serialized as String, I know that String is the default representation of a Enum (real class), but in this case is referenced as a interface EventType in AbstractDomainEvent.

When I try to read this document, I have this exception:

org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type [java.lang.String] to type [xxx.xxx.xxx.EventType]

Any idea? May be it's a bug? May be spring-data-mongo should resolve this situation inserting a metadata information about the concrete Enum instance, like a "_class" field?

I try insert @JsonTypeInfo annotation in EventType attribute at AbstractDomainEvent but it doesnt works, i think that it's ignored.

The temporary solution might be write a custom converter, but i think that this feature can be a framework feature.

Thanks in advcance!

Reference URL: https://stackoverflow.com/questions/48910761/deserializing-interfaces-with-spring-data-mongodb