CODEWITHSUNDEEP
javajsonjackson
shahaf
shahaf

Reputation: 4973

How to define 2-level inheritance structure with Jackson

I have the following base (interface) structure

@JsonTypeInfo(
        use = JsonTypeInfo.Id.NAME,
        property = "messageType",
        visible = true)
@JsonSubTypes({
        @JsonSubTypes.Type(value = AppMessage.class, name = "APP"),   
        @JsonSubTypes.Type(value = NotificationMessage.class, name = "NOTIFICATION"),
})
public interface Message {
    MessageType getMessageType();

    Date getTimestamp();
}

the AppMessage class is a simple POJO (for now) like

public class AppMessage implements Message {

    private String appId; 
    ...
    private Date timestamp = Date.from(Instant.now());

}

but the NotificationMessage is another interface

@JsonTypeInfo(
        use = JsonTypeInfo.Id.NAME,
        property = "NotificationType",
        visible = true)
@JsonSubTypes({
        @JsonSubTypes.Type(value = NotificationAckMessage.class, name = "ACK"),
        @JsonSubTypes.Type(value = NotificationReqMessage.class, name = "REQ"),
})
public interface NotificationMessage extends Message {

    String getDest();
    String getMessage();
    MessageType getMessageType();
    NotificationType getNotificationType();
}

and of course two more pojos as NotificationAckMessage and NotificationReqMessage classes which implements NotificationMessage.

When ever I want to deserialize NotificationMessage like

{"NotificationType": "REQ", "dest": "some dest", "message": "some message", "messageType": "NOTIFICATION", "notificationType": "REQ", "timestamp": 1584299876847}

ObjectMapper objectMapper = new ObjectMapper();
Message msg = objectMapper.readValue(msgStr, Message.class);

I get

Can not construct instance of NotificationMessage: abstract types either need to be mapped to concrete types, have custom deserializer, or contain additional type information

of course the AppMessage getting parsed without any errors.

How can I achieve this kind of structure and logic without flatten it, i.e define all the subtypes at the Message annotation level?

Thanks!

Upvotes: 3

Views: 1167

Answers (1)

Ilya Lysenko
Ilya Lysenko

Reputation: 1892

It seems that this is not supported. Look at this issue: https://github.com/FasterXML/jackson-databind/issues/374

The last answer:

It is not supported and there are no plans to support it. Do not design your system assuming this will be implemented.

Upvotes: 6

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