Enhanced Spring Data Rest delivers empty relations - spring

Question

in my current implementation using Spring-Boot, -HATEOAS, -Rest-Data I'm trying to spare some further rest calls and enhance my rest resource for credits to also deliver relations of a credit (see below account as ManyToOne and creditBookingClassPayments as OneToMany).
The problem now is that I'm not able to get it run. The call always delivers empty relations. I really would appreciate some help on this.
Here are the surroundings:
Credit.java
#Entity
#Getter
#Setter
public class Credit {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Setter(NONE)
#Column(name = "id")
private Long itemId;
#ManyToOne(fetch=FetchType.LAZY)
#JoinColumn(name="account_id", nullable = false)
private Account account;
#OneToMany(mappedBy = "credit")
private List<CreditBookingClassPayment> creditBookingClassPayments = new ArrayList<>();
#NotNull(message="Please enter a valid short name.")
#Column(length = 10, nullable = false)
private String shortName;
#NotNull(message="Please enter a valid name.")
#Column(nullable = false)
private String name;
...
}
CreditRepositoryCustomImpl.java
uses QueryDsl to enhance the credit resource with its realation
...
#Override
public List<Credit> findDistinctByAccountItemIdNew(Long accountId) {
QCredit credit = QCredit.credit;
QAccount account = QAccount.account;
QCreditBookingClassPayment creditBookingClassPayment = QCreditBookingClassPayment.creditBookingClassPayment;
QBookingClass bookingClass = QBookingClass.bookingClass;
BooleanExpression hasAccountItemId = credit.account.itemId.eq(accountId);
List<Credit> credits = from(credit).where(hasAccountItemId)
.innerJoin(credit.account, account)
.leftJoin(credit.creditBookingClassPayments, creditBookingClassPayment)
.leftJoin(creditBookingClassPayment.bookingClass, bookingClass).groupBy(credit.itemId).fetch();
return credits;
}
...
CreditController.java
looking into responseBody here all (account and credit payments) is available for credits
#RepositoryRestController
public class CreditController {
#Autowired
private CreditRepository creditRepository;
#RequestMapping(value = "/credit/search/findAllByAccountItemIdNew", method= RequestMethod.GET, produces = MediaTypes.HAL_JSON_VALUE)
#ResponseBody
public ResponseEntity<Resources<PersistentEntityResource>> findAllByAccountItemIdNew(#RequestParam Long accountId, PersistentEntityResourceAssembler persistentEntityResourceAssembler) {
List<Credit> credits = creditRepository.findDistinctByAccountItemIdNew(accountId);
Resources<PersistentEntityResource> responseBody = new Resources<PersistentEntityResource>(credits.stream()
.map(persistentEntityResourceAssembler::toResource)
.collect(Collectors.toList()));
return ResponseEntity.ok(responseBody);
}
}
CreditResourceIntegrTest.java
here creditResourcesEntity hold the credit but account is null and creditBookingClassPayment is an empty array
#Test
public void testFindAllByAccountItemId() throws URISyntaxException {
URIBuilder builder = new URIBuilder(creditFindAllByAccountItemIdRestUrl);
builder.addParameter("accountId", String.valueOf(EXPECTED_ACCOUNT_ID));
builder.addParameter("projection", "base");
RequestEntity<Void> request = RequestEntity.get(builder.build())
.accept(MediaTypes.HAL_JSON).acceptCharset(Charset.forName("UTF-8")).build();
ResponseEntity<Resources<Resource<Credit>>> creditResourcesEntity =
restTemplate.exchange(request, new ParameterizedTypeReference<Resources<Resource<Credit>>>() {});
assertEquals(HttpStatus.OK, creditResourcesEntity.getStatusCode());
//assertEquals(EXPECTED_CREDIT_COUNT, creditResourcesEntity.getBody().getContent().size());
}
Do I miss something?
Thanks for your help!
Karsten

Answer 1

Okay, PersistentEntityResourceAssembler doesn't support relations. But this could be handled by using projections.
CreditProjection.java
#Projection(name = "base" , types = Credit.class)
public interface CreditProjection {
String getShortName();
String getName();
List<CreditBookingClassPaymentProjection> getCreditBookingClassPayments();
BigDecimal getValue();
BigDecimal getInterestRate();
BigDecimal getMonthlyRate();
}
CreditBookingClassPaymentProjection.java
#Projection(name = "base" , types = CreditBookingClassPayment.class)
public interface CreditBookingClassPaymentProjection {
BookingClass getBookingClass();
CreditPaymentType getCreditPaymentType();
}
CreditController.java
#RepositoryRestController
public class CreditController {
#Autowired
private ProjectionFactory projectionFactory;
#Autowired
private CreditRepository creditRepository;
#RequestMapping(value = "/credit/search/findAllByAccountItemIdNew", method = RequestMethod.GET, produces = MediaTypes.HAL_JSON_VALUE)
#ResponseBody
public ResponseEntity<Resources<?>> findAllByAccountItemIdNew(#RequestParam Long accountId,
PersistentEntityResourceAssembler persistentEntityResourceAssembler) {
List<Credit> credits = creditRepository.findDistinctByAccountItemIdNew(accountId);
List<PersistentEntityResource> creditResources = new ArrayList<>();
for (Credit credit : credits) {
// credit.getCreditBookingClassPayments()
PersistentEntityResource creditResource = persistentEntityResourceAssembler.toResource(credit);
creditResources.add(creditResource);
}
Resources<CreditProjection> responseBody = new Resources<CreditProjection>(credits.stream()
.map(credit -> projectionFactory.createProjection(CreditProjection.class, credit))
.collect(Collectors.toList()));
return ResponseEntity.ok(responseBody);
}
}