How to take Object[] as return type in Spring DataJpa #Query methods? - spring-boot

Question

I want to fetch one row only by taking Object[] as return type in the #Query method of Repo interface. But while accessing the values it's showing
java.lang.ArrayIndexOutOfBoundsException: 1
If i will take Object (not Object[])as return type in the #Query method and while calling it again i have to cast return type to Object[] to get the values. But I don't understand why i can't take Object[] as return type directly.
Repo interface
public interface EmployeeRepository extends JpaRepository<Employee, Integer>{
#Query("select e.empName,e.empSal from org.st.model.Employee e where e.empId= ?1")
Object[] getData2(Integer eid);
}
Runner class
#Component
public class ConsoleRunner implements CommandLineRunner{
#Autowired
private EmployeeRepository repo;
public void run(String...strings) throws Exception{
Object[] obj = repo.getData2(106);//
System.out.println(obj[]);//No Exception no result but [Ljava.lang.Object;#68b366
System.out.println(obj[1]);//AIOBException
}
}
I should get name(String) and sal(Double) value as result.
#Query("select e.empName,e.empSal from org.st.model.Employee e where e.empId= ?1 ")
Object getData2(Integer eid);
Object[] obj = (Object[]) repo.getData2(106);
System.out.println(obj[1]);
It's working fine. cause i have taken Object as return type. But i dont understand why Object[] as Return type is showing AIOBE.

Answer 1

Java array indexes starts with 0. If your Object[] obj has length 1, you need to retrieve it like this: obj[0]
Try this:
public void run(String...strings) throws Exception{
Object[] obj = repo.getData2(106);
System.out.println(obj[]);
System.out.println(obj[0]);
}
}

Answer 2

java.lang.ArrayIndexOutOfBoundsException means you are trying to
access a array index that doesn't exist
Object[] results = repo.getData2(106);
for(Employee emp : results){
System.out.println(emp.getName() + " " + emp.getSal());
}
Employee class must have getters.
But using the List<Employee> makes type safety,
public interface EmployeeRepository extends JpaRepository<Employee, Integer>{
#Query("select e.empName,e.empSal from Employee e where e.empId= ?1")
List<Employee> getData2(Integer eid);
}
and you can easily access
List<Employee> results = repo.getData2(106);
for(Employee emp : results){
System.out.println(emp.getName() + " " + emp.getSal());
}

Answer 3

Returning Object[] means that the query returns an array of records. Each record is itself an Object[]. Therefore access the first column of the first record you need to use (Object[]) o[0]).
You probably want to use use a projection instead:
interface EmployeeView {
String getEmpName();
String getEmpSal();
}
#Query("select e.empName as empName, e.empSal as empSal from org.st.model.Employee e where e.empId= ?1")
EmployeeView getData2(Integer eid);
EmployeeView emp = repo.getData2(106);