java - 使用 @JsonSubTypes 进行反序列化以获得无值 - 缺少属性错误

Question

我这样反序列化 jsons:

{
  "type":"a",
  "payload" : {...}
}

有效负载类型取决于类型。我的类(class):

public class Sth<T extends Payload> {

    @JsonProperty("type")
    private String type;
    @Valid
    private T payload;

    @JsonTypeInfo(
        use = JsonTypeInfo.Id.NAME,
        include = JsonTypeInfo.As.EXTERNAL_PROPERTY,
        property = "type",
        visible = true,
        defaultImpl = NoClass.class)
    @JsonSubTypes({
        @JsonSubTypes.Type(value = APayload.class, name = "a"),
        @JsonSubTypes.Type(value = BPayload.class, name = "b"),
        @JsonSubTypes.Type(value = CPayload.class, name = "c")})
    public void setPayload(T payload) {
    this.payload = payload;
    }

    public void setType(String type) {
    this.type = type;
    }

}

我还输入了没有负载的“d”。如果我尝试反序列化:

{
  "type":"d",
  "payload" : null
}

它可以工作，但它不能在没有有效负载的情况下工作:

{
  "type":"d",
}

如何让它与上一个例子一起工作？

我得到的错误堆栈跟踪:

[error] Caused by: com.fasterxml.jackson.databind.JsonMappingException: Missing property 'payload' for external type id 'type
[error]  at [Source: N/A; line: -1, column: -1]
[error]     at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:164)
[error]     at com.fasterxml.jackson.databind.DeserializationContext.mappingException(DeserializationContext.java:700)
[error]     at com.fasterxml.jackson.databind.deser.impl.ExternalTypeHandler.complete(ExternalTypeHandler.java:160)
[error]     at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeWithExternalTypeId(BeanDeserializer.java:690)
[error]     at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeWithExternalTypeId(BeanDeserializer.java:639)
[error]     at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:266)
[error]     at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:124)
[error]     at com.fasterxml.jackson.databind.ObjectMapper._readValue(ObjectMapper.java:2965)
[error]     at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:1587)
[error]     at com.fasterxml.jackson.databind.ObjectMapper.treeToValue(ObjectMapper.java:1931)
[error]     at play.libs.Json.fromJson(Json.java:47)

Answer 1

有明确的反序列化功能:

new ObjectMapper().configure(
DeserializationFeature.FAIL_ON_MISSING_EXTERNAL_TYPE_ID_PROPERTY, 
false);