Jackson将额外字段反序列化为映射

Question

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

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

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

Answer 1

有一个特性和一个注释正好符合这个目的。

我进行了测试，它可以使用UUID，如您的示例所示：

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);
    }
}

它的工作原理如下：

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

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);
    }
}