英文:
How to define 2-level inheritance structure with Jackson
问题
我有以下基本（接口）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（目前如此），类似于
public class AppMessage implements Message {private String appId;...private Date timestamp = Date.from(Instant.now());}
但 NotificationMessage 是另一个接口
@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();}
当我想反序列化 NotificationMessage 时，像这样
{"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);
我得到
无法构造 NotificationMessage 的实例：抽象类型需要映射到具体类型，具有自定义反序列化程序，或包含附加类型信息
当然，AppMessage 在不出现任何错误的情况下解析。
如何在不展开它的情况下实现这种结构和逻辑，即在 Message 注解级别定义所有子类型？
谢谢！
英文:
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!
答案1
得分: 4
这似乎是不受支持的。看一下这个问题：https://github.com/FasterXML/jackson-databind/issues/374
最后的回答：
> 这不受支持，也没有支持的计划。不要设计你的系统，假设这将会被实现。
英文:
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.
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