杰克逊将额外的字段反序列化为地图

Question

我希望将JSON对象中的任何未知字段反序列化为地图中的条目,该地图是pojo的成员.

例如json

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

和pojo

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

有没有办法用杰克逊配置？如果没有,是否有一种有效的方法来编写StdDeserializer它(假设值unknownFields可以是更复杂但众所周知的一致类型)？

Answer 1

有一个功能和注释完全符合这个目的.

我测试过它和你的例子中的UUID一样:

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);

更常见的类型如字符串工作:

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);
    }
}

(我在这篇博文中首先发现了这个功能).