Project embedded document fields after lookup operation - spring

Question

I want to do a join between Timesheet:
#Data
#AllArgsConstructor
#NoArgsConstructor
#Document(collection = TIMESHEET_COLLECTION)
public class Timesheet {
#Id
private ObjectId id;
private ObjectId employeeId;
private LocalDate date;
private String occupationTitle;
private BigDecimal salary;
private List<TimesheetEntry> entries;
}
and Employee (as embedded document):
#Data
#AllArgsConstructor
#NoArgsConstructor
#Document(collection = Employee.EMPLOYEE_COL)
public class Employee {
#Id
private ObjectId id;
private String registry;
private String cpf;
private String firstName;
private String lastName;
private String nickname;
private String phone;
private LocalDate dateOfBirth;
private LocalDate admissionDate;
private EmployeeOccupation occupation;
private EmployeePaymentPreferences paymentPreferences;
private Map<String, String> equipmentPreferences;
private Boolean active;
}
So I have this aggregation query, with match, lookup, unwind and projection operations.
Aggregation aggregation = Aggregation.newAggregation(matchTimesheetFilter(timesheetFilter), lookupEmployee(), unwindEmployee(), projectEmployee());
There are lookup and unwind implementations. I'm unwinding because employee should be a single object, not an array.
private LookupOperation lookupEmployee(){
return LookupOperation.newLookup()
.from("employee")
.localField("employeeId")
.foreignField("_id")
.as("employee");
}
private UnwindOperation unwindEmployee(){
return Aggregation.unwind("employee");
}
It returns successfully a Timesheet document with a embedded Employee document. The point is: I don't want all data from employee. I only want a few fields.
So, I tried to exclude unwanted fields from employee, using my projection operation:
private ProjectionOperation projectEmployee() {
return Aggregation.project().andExclude("employee.nickname", "employee.firstName", "employee.fullName");
}
It didn't work. My embedded employee is still being returned with all fields. However I can successfully exclude fields from Timesheet, if I do something like this:
private ProjectionOperation projectEmployee() {
return Aggregation.project().andExclude("startDate", "endDate");
}
How can I project custom fields from a document embedded through a lookup operation?

Answer 1

i think you need to exclude "employee.nickname", "employee.firstName", "employee.fullName", instead of "nickname", "firstName", "fullName"
Try this:
private ProjectionOperation projectEmployee() {
return Aggregation.project().andExclude("employee.nickname", "employee.firstName", "employee.fullName");
}

Answer 2

i did it this way (not sure if it's right but it works):
private LookupOperation lookupEmployee(){
return LookupOperation.newLookup()
.from("employee")
.localField("employeeId")
.foreignField("_id")
.as("employeeLookup");
}
no unwind used
Aggregation.project().and("employeeLookup.firstName").as("employee.firstName")