使用Jackson反序列化JSON的问题

Question

I have such 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}

I would like to deserialize it to Java class but I am interested in only some JSON fields. Anyway here are the model classes:

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[];

}

etc.

But for some reason I get following exception:

org.codehaus.jackson.map.exc.UnrecognizedPropertyException: Unrecognized field "body" (Class com.demo.Response), not marked as ignorable at [Source: java.io.StringReader@6483f5ae; line: 1, column: 10] (through reference chain: com.demo.Response["body"])

Here is code(the JSON string is correctly received and has same format as I initially mentioned in the beginning):

 String res = MainProgram.sendGet("someURL");

 ObjectMapper objectMapper = new ObjectMapper();
 Response ob = objectMapper.readValue(res, Response.class);

I would appreciate some help.

Answer 1

You need to create getters and setters for the fields, and you should add annotations to your fields.

Annotation:

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

Doing one of above will make it work.

Sidenote:

You can create your pojos from json automatically with http://www.jsonschema2pojo.org/ . Just paste it in and download it, or use one of their plugins.

Answer 2

As mentioned by others, private fields are not auto-detect by default, so either:

• Annotating fields with @JsonProperty OR
• Adding setter

is needed for deserialization.

However, there is another possibility: you can use annotations @JsonAutoDetect to change minimum visibility needed, and here enable discovery of ALL fields. Or you can even change the defaults used via ObjectMapper method (something like setVisibility(...) ).