Custom query result

Sometimes you don't want to select entire entity. EzyJPA will help you map query result to a result class.

1. Query

Let's say we have query method like this: 
@EzyQuery(
    value = "select employeeId, firstName from ezyfox_jpa_employee where employeeId = ?0",
    nativeQuery = true
)
Optional<EmployeeIdAndFirstNameResult> findEmployeeIdAndFirstNameByEmployeeIdOptional(
    String employeeId
);
Let's focus on select employeeId, firstName, we select 2 fields in camel case.

2. Result class

With 2 above fields, we will need create a class with 2 fields same name and same order, example: 
@Getter
@Setter
@EzyQueryResult
public class EmployeeIdAndFirstNameResult {
    private String employeeId;
    private String firstName;
}
Don't for get @EzyQueryResult annotation, EzyJPA will need this annotation to recognize the result class and create deserializer class for it.

3. Use cases

You can use request class in 3 cases:
  • Find one nullable result, example: EmployeeIdAndFirstNameResult findEmployeeIdAndFirstNameByEmployeeId
  • Find one optional result, example: Optional<EmployeeIdAndFirstNameResult> findEmployeeIdAndFirstNameByEmployeeIdOptional
  • Fine a list result, example: List<EmployeeIdAndFirstNameResult> findEmployeeIdAndFirstNameListByEmployeeId

Next

You can see how to connect to multi datasources