findAll

Service

public List<DepartmentDTO> findAll() {
    List<Department> departments = departmentRepository.findAll();

    return departments.stream().map(DepartmentDTO::new).toList();
}

Controller

@GetMapping
public ResponseEntity<List<DepartmentDTO>> findAll() {
    List<DepartmentDTO> dto = departmentService.findAll();
    return ResponseEntity.ok().body(dto);
}