How to get current time in java enterprise and be easily testable
With Java version 8 it’s very easy to get the current timestamp with LocalDateTime.now().
One problem that might arise is it’s not easily testable/mockable.
Imagine some testing data and conditions depend on the date you set through this call, or you want to do “time travel”.
The solution is quite simple - define a service class that produces the current timestamp, which you can then easily mock,
in this case we’ll name it ProductionCalendar:
@ApplicationScoped
public class ProductionCalendar {
public LocalDateTime currentTimestamp() {
return LocalDateTime.now();
}
public LocalDate currentDate() {
return LocalDate.now();
}
public String currentTimestamp(Partner partner) {
return DateTimeFormatter.ofPattern("yyyy-MM-dd-HH.mm.ss.SSSSSS")
.format(LocalDateTime.now());
}
}
Then when were you need to call LocalDateTime.now() inject this service and use its methods instead:
@Stateless
public class PartnerRepository {
@Inject ProductionCalendar productionCalendar;
@Inject EntityManager entityManager;
public void savePartner(String partnerNumber) {
Partner partner = new Partner();
partner.setPartnerNumber(partnerNumber);
partner.setCreatedAt(productionCalendar.currentTimestamp());
entityManager.persist(partner);
}
public List<Partner> getPartnerCreatedAfterDate(LocalDateTime timestamp) {
String queryJpql = "select p from P p where createdAt > :timestamp order by createdAt desc";
TypedQuery<Partner> query = entityManager.createQuery(queryJpql, Partner.class);
query.setParameter("timestamp", timestamp);
return query.getResultList();
}
}
Then, in the test class you can easily mock ProductionCalendar and calls to its methods and set timestamps as we need them:
@ExtendWith(MockitoExtension.class)
@RunWith(JUnitPlatform.class)
public class UserServiceUnitTest {
@Inject PartnerRepository partnerRepository;
@Mock ProductionCalendar productionCalendar;
@Test
void testGetLatestPartners() {
when(productionCalendar.currentTimestamp()).thenReturn(LocalDatetime.now().minusDays(1));
partnerRepository.save("12345");
var recentPartners = partnerRepository.getPartnerCreatedAfterDate(LocalDatetime.now().minusDays(2));
assertThat(recentPartners, hasSize(1));
}
}
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