Jackson 将额外的字段反序列化为 Map [英] Jackson deserialize extra fields as Map

问题描述

我希望将 JSON 对象中的任何未知字段反序列化为 Map 中的条目，Map 是 POJO 的成员.

I'm looking to deserialize any unknown fields in a JSON object as entries in a Map which is a member of a POJO.

例如，这里是 JSON:

For example, here is the JSON:

{
  "knownField" : 5,
  "unknownField1" : "926f7c2f-1ae2-426b-9f36-4ba042334b68",
  "unknownField2" : "ed51e59d-a551-4cdc-be69-7d337162b691"
}

这是 POJO:

class MyObject {
  int knownField;
  Map<String, UUID> unknownFields;
  // getters/setters whatever
}

有没有办法用 Jackson 配置它?如果没有，是否有一种有效的方法来编写 StdDeserializer 来完成它(假设 unknownFields 中的值可以是更复杂但众所周知的一致类型)?

Is there a way to configure this with Jackson? If not, is there an effective way to write a StdDeserializer to do it (assume the values in unknownFields can be a more complex but well known consistent type)?

推荐答案

有一个特性和注释正好符合这个目的.

There is a feature and an annotation exactly fitting this purpose.

我进行了测试，它可以与您的示例中的 UUID 一起使用:

I tested and it works with UUIDs like in your example:

class MyUUIDClass {
    public int knownField;

    Map<String, UUID> unknownFields = new HashMap<>();

    // Capture all other fields that Jackson do not match other members
    @JsonAnyGetter
    public Map<String, UUID> otherFields() {
        return unknownFields;
    }

    @JsonAnySetter
    public void setOtherField(String name, UUID value) {
        unknownFields.put(name, value);
    }
}

它会像这样工作:

    MyUUIDClass deserialized = objectMapper.readValue("{" +
            ""knownField": 1," +
            ""foo": "9cfc64e0-9fed-492e-a7a1-ed2350debd95"" +
            "}", MyUUIDClass.class);

还有更常见的类型，比如字符串:

Also more common types like Strings work:

class MyClass {
    public int knownField;

    Map<String, String> unknownFields = new HashMap<>();

    // Capture all other fields that Jackson do not match other members
    @JsonAnyGetter
    public Map<String, String> otherFields() {
        return unknownFields;
    }

    @JsonAnySetter
    public void setOtherField(String name, String value) {
        unknownFields.put(name, value);
    }
}

(我发现首先在这篇博文中介绍这个功能).

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