Null response values from REST API using restTemplate

Question

I created a Mock service that return JSON response as below :

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

Then i created the GetRegionsDistrictsRestClient class to consume the REST API using restTemplate :

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;
}

}

The RegionRequestHeader and DistrictRequestHeader are like this :

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;
}

}

The Response is ok but the values are null as mentioned on screenshot :

Answer 1

Since you have a different property name within the class. Spring automatic deserialization won't map the fields correctly with the response JSON structure.

If this is the response body

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

Then, You need to define JSON property names explicitly in the class

public class RegionRequestHeader {

@JsonProperty("RegionsID")
private Integer regionsID;

@JsonProperty("RegionsName")
private String regionsName;

@JsonProperty("DistrictList")
private List<DistrictRequestHeader> districtList;

// Getters & Setters
}

Similarly,

public class DistrictRequestHeader {
 @JsonProperty("DistrictsID")
 private Integer districtsID;

 @JsonProperty("DistrictsName")
 private String districtsName;
 //Getters & Setters
}