Java jackson throw JsonMappingException无法构造的实例

//接口

public interface NotificationPayload {
}

public ClassA implements NotificationPayload {...}
public ClassB implements NotificationPayload {...}
...
public ClassX implements NotificationPayload {...}

//类实现接口

public ClassA implements NotificationPayload {...}
public ClassB implements NotificationPayload {...}
...
public ClassX implements NotificationPayload {...}

//要发送的消息

public class Notification<T extends NotificationPayload> {
    private T data; //T may be ClassA/ClassB/ClassC.../ClassX
    ...
}

我将其转换为：

Notification notif = objectMapper.readValue(json, Notification.class);

它会引发异常：

java.lang.IllegalArgumentException: Can not construct instance of 
com.common.kafka.notification.NotificationPayload: abstract types
either need to be mapped to concrete types, have custom deserializer, or
contain additional type information
at [Source: N/A; line: -1, column: -1] (through reference chain:
com.common.kafka.notification.Notification["data"])

---

我已经阅读了这个问题：但它似乎帮不上忙，因为我有太多的类从接口实现，而不仅仅是一次。

您需要使用jackson的注释来实现多态反序列化

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME,
        include = JsonTypeInfo.As.PROPERTY, property = "type")
@JsonSubTypes({
        @JsonSubTypes.Type(value = ClassA.class, name = "ClassA"),
        @JsonSubTypes.Type(value = ClassB.class, name = "ClassB")
})
public interface NotificationPayload {
}

public class ClassA implements NotificationPayload {

    private Integer userId;

    public Integer getUserId() {
        return userId;
    }

    public void setUserId(Integer userId) {
        this.userId = userId;
    }
}

public class Notification <T extends NotificationPayload> {

    private T data; //T may be ClassA/ClassB/ClassC.../ClassX

    @JsonCreator
    public Notification(T data) {
        this.data = data;
    }

    public static void main(String[] args) throws IOException {

        String jsonStr = "{\"type\":\"ClassB\",\"userId\":10087}";

        ObjectMapper objectMapper = new ObjectMapper();
        Notification notification = objectMapper.readValue(jsonStr, Notification.class);
    }
}

@JsonTypeInfo（use=JsonTypeInfo.Id.NAME，
include=JsonTypeInfo.As.PROPERTY，PROPERTY=“type”）
@JsonSubTypes({
@JsonSubTypes.Type（value=ClassA.class，name=“ClassA”），
@JsonSubTypes.Type（value=ClassB.class，name=“ClassB”）
})
公共接口通知有效负载{
}
公共类ClassA实现NotificationPayload{
私有整数用户标识；
公共整数getUserId（）{
返回用户标识；
}
public void setUserId（整数userId）{
this.userId=userId；
}
}
公开课通知{
私有T数据；//T可以是ClassA/ClassB/ClassC…/ClassX
@JsonCreator
公共通知（T数据）{
这个数据=数据；
}
公共静态void main（字符串[]args）引发IOException{
字符串jsonStr=“{\'type\'：\'ClassB\'，\'userId\'：10087}”；
ObjectMapper ObjectMapper=新的ObjectMapper（）；
Notification Notification=objectMapper.readValue（jsonStr，Notification.class）；
}
}

您可以找到的所有注释