Enhanced Spring Data Rest delivers empty relations

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);
    }

}