使用杰克逊反序列化 JSON 时出现问题

Question

我有这样的JSON

{"body":{"result":[{"crossStateId":1,"raceId":181564,"withOfficer":1,"documents":[{"indexed":0,"documentNumber":"zzz","isMain":1,"documentTypeId":6,"serverId":16,"countryId":327,"useDate":"2017-02-07T19:31:51.000+0000","documentSubTypeId":6,"crossId":5018177,"documentId":44973231,"personId":222,"infinity":0,"documentValid":"2023-08-25T20:00:00.000+0000"}],"directionId":2,"documentNumber":"sss","operatorUsername":"AIRPORT_84","crossDate":"2017-02-07T19:31:51.000+0000","serverId":16,"crossTypeId":1,"crossRegisterDate":"2017-02-07T19:31:52.818+0000","officerNote":"","children":[],"personNote":"","crossId":5018177,"workplaceId":82,"divisionId":2,"race":{"carriageContainer":0,"raceId":181564,"raceStateId":1,"directionId":2,"creatorId":415,"countryId":327,"transportIdByType":605,"raceDateTime":"2017-02-07T19:20:58.000+0000","raceNumber":"841 sss sss","creatorUsername":"AIRPORT_8","divisionId":2,"transportTypeId":3,"createDate":"2017-02-07T19:20:58.000+0000"},"syncState":0,"autos":[],"userId":491,"raceNumber":"841 sss sss","operatorNote":"","person":{"firstNameEn":"JUMBERI","indexed":1,"lastNameGe":"ჩოხელი","genderId":2,"personId":6027803,"personalNumber":"222","countryNameGe":"sss","birthDate":"1963-06-14T20:00:00.000+0000","lastNameEn":"sss","countryId":327,"firstNameGe":"sss"},"airplane":{"raceNumber":"841 sss sss","airCompanyId":1,"airplaneId":605,"airportId":5657,"bortNumber":"01","transportSubTypeId":78,"countryId":360},"underAge":0,"personId":6027803,"decisionId":22}],"total":8264},"errorCode":0}

我想将其反序列化为 Java 类，但我只对一些 JSON 字段感兴趣。无论如何，这里是模型类：

public class Response implements Serializable {
    private Body body;
    private long errorCode;
}
public class Body implements Serializable {
    Result result[];
}
public class Result implements Serializable {
    private long crossStateId;
    private long raceId;
    private Person person;
    private Child children [];
    private Auto autos[];
}

等。

但是由于某种原因，我得到了以下异常：

org.codehaus.jackson.map.exc.UnrecognizedPropertyException： 无法识别的字段"body"(类 com.demo.Response(，未标记为 在 [来源： java.io.StringReader@6483f5ae; 行： 1， 列： 10](通过参考链：com.demo.Response["body"](

这是代码(JSON字符串被正确接收，并且格式与我在开头最初提到的相同(：

 String res = MainProgram.sendGet("someURL");
 ObjectMapper objectMapper = new ObjectMapper();
 Response ob = objectMapper.readValue(res, Response.class);

我将不胜感激。

Answer 1

您需要为字段创建 getter 和 setter，并且应该向字段添加注释。

注解：

@JsonProperty(value = "body")
private Body body;

执行上述操作之一将使其正常工作。

旁注：

您可以使用 http://www.jsonschema2pojo.org/从 json 自动创建 pojo。只需将其粘贴并下载，或使用他们的插件之一。

Answer 2

正如其他人提到的，默认情况下不会自动检测private字段，因此：

• 使用 @JsonProperty OR 注释字段
• 添加二传手

是反序列化所必需的。

但是，还有另一种可能性：您可以使用注释@JsonAutoDetect来更改所需的最小可见性，并在此处启用所有字段的发现。或者您甚至可以通过ObjectMapper方法更改使用的默认值(例如 setVisibility(...) (。