java - 如何用 Jackson 定义 2 级继承结构

Question

我有以下基本(接口(interface))结构

@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();
}

AppMessage类是一个简单的 POJO(现在)，比如

public class AppMessage implements Message {

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

}

但是 NotificationMessage是另一个界面

@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();
}

当然还有两个 pojo 为 NotificationAckMessage和 NotificationReqMessage实现 NotificationMessage 的类.

每当我想反序列化 NotificationMessage像

{"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);

我明白了

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

当然是 AppMessage得到解析没有任何错误。

如何在不展平的情况下实现这种结构和逻辑，即在 Message 处定义所有子类型注释级别？

谢谢!

Answer 1

似乎不支持此功能。看这个问题:https://github.com/FasterXML/jackson-databind/issues/374

最后一个答案:

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