@JsonTypeResolver是使用多个属性进行解析的唯一选项吗? [英] Is @JsonTypeResolver the only option for resolving using multiple properties?

问题描述

我有以下格式的传入JSON数据

I have incoming JSON data in the following format

{
    "header": {
        "schema_id": {
            "namespace": "omh",
            "name": "physical-activity",
        },
    },
    "body": {
        "activity_name": "walking",
        "distance": {
            "value": 1.5,
            "unit": "mi"
        },
    }
}

以及类似的Java类

public class DataPoint<T extends Measure> {

    private DataPointHeader header;
    private T body;

和

@JsonNaming(LowerCaseWithUnderscoresStrategy.class)
public class PhysicalActivity extends Measure {

    private String activityName;
    private LengthUnitValue distance;

我希望Jackson根据JSON文档中的schema_id将body解析为PhysicalActivity类型，例如用伪代码

I'd like Jackson to resolve body to the PhysicalActivity type based on the schema_id in the JSON document, e.g. in pseudocode

if schema_id.namespace == 'omh' && schema_id.name == 'physical-activity'
     then return PhysicalActivity.class

我尝试使用@JsonTypeIdResolver进行此操作，但是如果尝试使用@JsonTypeInfo导航到header.schema_id.name，例如

I've tried doing this with @JsonTypeIdResolver but if I try to navigate to header.schema_id.name with @JsonTypeInfo, e.g.

@JsonTypeInfo(use = JsonTypeInfo.Id.CUSTOM,
        include = JsonTypeInfo.As.EXTERNAL_PROPERTY,
        property = "header.schema_id.name")
@JsonTypeIdResolver(DataPointTypeIdResolver.class)
public abstract class Measure {

我收到一个missing property: 'header.schema_id.name'错误.即使可以，我也不认为我可以同时决定namespace和name属性.

I get a missing property: 'header.schema_id.name' error. And even if I could, I don't think I can take a decision on both the namespace and name properties.

除了使用@JsonTypeResolver从头开始构建之外，还有其他明智的方法吗?

Is there a sane way to do this besides building from scratch with @JsonTypeResolver?

推荐答案

否，无法使用路径表达式来匹配属性.这将需要访问完整的JSON(子树).

No, there is no way to use path expressions for matching properties. This would require access to the full JSON (sub-tree).

对于Jackson 2.5，将类型ID设为标量值(通常是字符串)的要求稍有放松，因此可能支持JSOG .有关此问题的更多背景信息:

With Jackson 2.5, there is slight relaxation from requirement for type ids to be scalar values (usually Strings), so that JSOG may be supported. More background is on this issue:

https://github.com/FasterXML/jackson-databind/issues/622

但是我认为这还远远不足以让您使用标准的Jackson类型id解析.

But I don't think that is far enough to let you use standard Jackson type id resolution.

您可能会考虑的一件事是Creator方法，例如:

One thing you might consider are Creator methods, something like:

abstract class Measure {
   // either constructor, or static method:
   @JsonCreator
   public static Measure construct(
     @JsonProperty("header") HeadOb header, // or JsonNode, Map etc
     @JsonProperty("body") JsonNode body) {
        // extract type info, build actual instance from body
     }
}

或Converter，其中您使用中间包装器进行标头绑定，而主体仅绑定到JsonNode或Map，然后从那里构造.

or, perhaps Converter where you use an intermediate wrapper to header bound, and body only bound to JsonNode or Map, and then construct from there.

这篇关于@JsonTypeResolver是使用多个属性进行解析的唯一选项吗?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！