java - jackson 的嵌套映射

Question

我收到一个 JSON 字符串作为响应，如下所示

 {"size":3,"page-size":3,"subscribers-aircraft":
[
{"company-name":"ATCOMPANYTEST","tailno":"N345","status":"ACTIVE","network-status":"ACTIVE","id":18501,"contact":"SS Theairtime","model":"A-380-800","note":null,"created-at":"Jun 29, 2015 7:42:54 AM","packages":2,"username":"ATAIRCRAFTTEST","external-account":null,"consumer-type":"AIRCRAFT","isp-id":18493,"parent-id":18497,"subscriber-feature-id":13,"status-code":null,"status-msg":null},
{"company-name":"The AIRTIME 3","tailno":"VT456","status":"ACTIVE","network-status":"ACTIVE","id":18489,"contact":"Ramesh Anantarapu","model":"C-21","note":null,"created-at":"Jun 25, 2015 8:27:16 AM","packages":0,"username":"ramesh23","external-account":null,"consumer-type":"AIRCRAFT","isp-id":18469,"parent-id":18473,"subscriber-feature-id":9,"status-code":null,"status-msg":null},
{"company-name":"The AIRTIME 3","tailno":"VT23","status":"ACTIVE","network-status":"OFFLINE","id":18485,"contact":"Ramesh Anantarapu","model":"747-100","note":null,"created-at":"Jun 23, 2015 2:49:15 PM","packages":1,"username":"ramesh","external-account":null,"consumer-type":"AIRCRAFT","isp-id":18469,"parent-id":18473,"subscriber-feature-id":5,"status-code":null,"status-msg":null}],
"status-code":"AIRTIME-P4000","status-msg":"Successfully"}

这是一个平淡的回应。

我现在正努力将其映射到名为 AircraftInfo 的顶级 POJO，其中包含另外两个 POJO 作为其实体。

虽然例如:company-name、tailNo 和 status 直接属于 AircraftInfo，而 user-name、id 属于 UserInfo POJO，它是 AircraftInfo 中的一个实体。

由于 JSON 响应是扁平的，因此实际上不可能将这样的响应映射到嵌套结构中。

有人可以建议最优雅的实现方式吗？

Answer 1

一个选择是使用 @JsonCreator annotation :

public static class AircraftInfo {

    private final String companyName;

    private final String tailNo;

    private final UserInfo userInfo;

    @JsonCreator
    public AircraftInfo(Map<String, Object> flatProperties) {
        this.companyName = (String) flatProperties.get("company-name");
        this.tailNo = (String) flatProperties.get("tailno");
        UserInfo user = new UserInfo();
        user.setUserName((String) flatProperties.get("username"));
        user.setId((Integer) flatProperties.get("id"));
        this.userInfo = user;
    }

    // getters for final fields
}

UserInfo 类如下:

public class UserInfo {

    private String userName;

    private int id;

    // getters and setters
}

您可以将 JSON 反序列化为以下 Response POJO:

public class Response {

    private int size;

    @JsonProperty("page-size") // non standard JSON property name
    private int pageSize;

    @JsonProperty("subscribers-aircraft") // non standard JSON property name
    private List<AircraftInfo> subscribersAircraft; // use class defined above!

    @JsonProperty("status-code") // non standard JSON property name
    private String statusCode;

    @JsonProperty("status-msg") // non standard JSON property name
    private String statusMsg;

    // getters and setters
}

您可以按如下方式使用这两个类:

ObjectMapper mapper = new ObjectMapper();
mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
mapper.setSerializationInclusion(Include.NON_NULL);
String json = // your exact json here, ESCAPED!
Response response = mapper.readValue(json, Response.class);

response 实例现在应该按照您的要求构建，尽管您的 JSON 是扁平结构。