@EnableRedisRepositories
public interface CustomerRepository extends JpaRepository<Customer, String> {

   Optional<Customer>  findByFirstName(String firstName);
}

@Service
@Transactional
public class CustomerService {
    private final CustomerRepository repository;

    public CustomerService(CustomerRepository repository) {
        this.repository = repository;
    }

   ...


      public Optional<Customer> retrieveCustomersByName(String name) {
            return repository.findByFirstName(name);
        }
}

@RestController
@RequestMapping("/customers")
public class CustomerController {

    @Autowired
    private CustomerService customerService;

 ....

    @GetMapping("/{firstName}")
    public ResponseEntity<?> getCustomers(@PathVariable String firstName) {
        Optional<?> customer = customerService.retrieveCustomersByName(firstName);
        if (!customer.isPresent()) {
            return ResponseEntity.badRequest().build();
        }
        return ResponseEntity.ok(customer);
    }


}