Getting Null Values in Spring Native Query Project - spring-boot

Question

This is my Data Repository file and i used native query to retrieve all data address(Locations) of Data. I called the function using Postman and I got null outputs of locations. This my first time of using Native query and its really impossible to solve these errors
DataRepository
public interface DataRepository extends JpaRepository<Data, Long> {
#Query(value = "SELECT dataAddress FROM Data")
List<DataProject> getDataAddress();
}
DataServiceImpl
public List<DataProject> getDataAddress() {
return dataRepository.getDataAddress();
}
DataService
List<DataProject> getDataAddress();
DataModel
#Entity
#Table(name = "CCCData")
public class Data {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private long dataId;
#Column(name = "DATA_NAME")
private String dataName;
#Column(name ="DATA_ADDRESS")
private String dataAddress;
#Column(name = "DATA_DESC")
private String dataDesc;
#CreationTimestamp
private Date dateOfCreated;
#CreationTimestamp
private Date dateOfUpdated;
public long getDataId() {
return dataId;
}
public void setDataId(long dataId) {
this.dataId = dataId;
}
public String getDataName() {
return dataName;
}
public void setDataName(String dataName) {
this.dataName = dataName;
}
public String getDataAddress() {
return dataAddress;
}
public void setDataAddress(String dataAddress) {
this.dataAddress = dataAddress;
}
public String getDataDesc() {
return dataDesc;
}
public void setDataDesc(String dataDesc) {
this.dataDesc = dataDesc;
}
public Date getDateOfCreated() {
return dateOfCreated;
}
public void setDateOfCreated(Date dateOfCreated) {
this.dateOfCreated = dateOfCreated;
}
public Date getDateOfUpdated() {
return dateOfUpdated;
}
public void setDateOfUpdated(Date dateOfUpdated) {
this.dateOfUpdated = dateOfUpdated;
}
DataProjection
public interface DataProject {
String getDataAddress();
}
DataController
#GetMapping("/data/locations")
public List<DataProject> getDataAddress() {
return dataService.getDataAddress();
}
Postman Output
[
{
"dataAddress": null
},
{
"dataAddress": null
},
{
"dataAddress": null
},
{
"dataAddress": null
}
]

Answer 1

Spring won't return you only address using below query. It still return you DATA object
public interface DataRepository extends JpaRepository<Data, Long> {
#Query(value = "SELECT dataAddress FROM Data")
List<DataProject> getDataAddress();
}
for fetching only DataAddress you need to create a constructor inside Data model for DataAddress only
public Data(String dataAddress) {
this.dataAddress = dataAddress;
}
and your query will look like this:
public interface DataRepository extends JpaRepository<Data, Long> {
#Query(value = "SELECT new Data(dataAddress) FROM Data")
List<DataProject> getDataAddress();
}
Update 1 :
if you need this for other fields with same datatype and then above 'constructor' based method fails. There are some other alternatives:
You can fetch DATA object and use java stream map function to extract only 1 field. data.stream().map((data) -> data.getDataAddress()).collect(Collectors.toList())
You can use native SQL query to fetch only required fields.
#Query(value = "SELECT d.data_address FROM CCCData d", nativeQuery=true)