使用restTemplate的REST API的响应值为空

我创建了一个Mock服务，该服务返回JSON响应，如下所示：

{“ RegionsID”：“ 123”，“ RegionsName”：“ TestRegion”，“ DistrictList”：[{“ DistrictsID”：“ 321”}，{“ DistrictsName”：“ TestDistrict”}]}

然后，我创建了GetRegionsDistrictsRestClient类，以使用restTemplate使用REST API：

public class GetRegionsDistrictsRestClient {

private Logger logger = Logger.getLogger(getClass().getName());

@Autowired
public RegionRequestHeader getRegionDistrict() {

    String theUrl = "https://a03e1a89-0363-4b17-8e3c-eb0220020e9b.mock.pstmn.io/GetRegionsDistricts";

    RestTemplate restTemplate = new RestTemplate();

    RegionRequestHeader result = restTemplate.getForObject(theUrl, RegionRequestHeader.class);

    return result;
}

}

RegionRequestHeader和DistrictRequestHeader如下所示：

public class RegionRequestHeader {

private Integer regionsID;

private String regionsName;

private List<DistrictRequestHeader> districtList;

public Integer getRegionsID() {
    return regionsID;
}

public void setRegionsID(Integer regionsID) {
    this.regionsID = regionsID;
}

public String getRegionsName() {
    return regionsName;
}

public void setRegionsName(String regionsName) {
    this.regionsName = regionsName;
}

public List<DistrictRequestHeader> getDistrictList() {
    return districtList;
}

public void setDistrictList(List<DistrictRequestHeader> districtList) {
    this.districtList = districtList;
}

}

public class DistrictRequestHeader {

private Integer districtsID;

private String districtsName;

public Integer getDistrictsID() {
    return districtsID;
}

public void setDistrictsID(Integer districtsID) {
    this.districtsID = districtsID;
}

public String getDistrictsName() {
    return districtsName;
}

public void setDistrictsName(String districtsName) {
    this.districtsName = districtsName;
}

}

响应还可以，但是如屏幕截图所示，值为空：