Specification Example

AppService.java

  public List<AppResponseVO> findLatestAndSubmittedAppsByAppId() {
        return appRequestRepository.findAll(this::buildSpecification).stream()
                .map(AppResponseVO::new)
                .sorted(Comparator.comparing((AppResponseVO appResponse) -> {
                    switch (AppLifeCycleStatus.valueOf(appResponse.getStatus())) {
                        case IN_REVIEW:
                            return 1;
                        case ONLINE:
                            return 2;
                        case REJECTED:
                            return 3;
                        default:
                            return 9;
                    }
                }).thenComparing(Comparator.comparing(AppResponseVO::getLastUpdatedTime).reversed()))
                .collect(Collectors.toList());
    }
/*
    public List<AppResponseVO> findAppsByOrganizationId(Integer organizationId) {
        return appRequestRepository.findAll(this::buildSpecification).stream()
                .map(AppResponseVO::new)
                .collect(Collectors.toList());
    }
*/
    private Predicate buildSpecification(Root<AppRequest> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
        Path<AppRequest.AppRequestStatus> appRequestStatusPath = root.get("status");

        Subquery<Long> latestAppSubQuery = query.subquery(Long.class);
        Root<AppRequest> subAppRequest = latestAppSubQuery.from(AppRequest.class);

        Expression<Long> latestAppModifyTime = cb.greatest(subAppRequest.<Long>get("lastUpdateTime"));
        Expression<String> appIdRoot = root.get("appId");
        Expression<String> appIdSubApp = subAppRequest.get("appId");
        Expression<Long> modifyTimeRoot = root.get("lastUpdateTime");

        Predicate appId = cb.equal(appIdRoot, appIdSubApp);

        latestAppSubQuery.select(latestAppModifyTime);
        latestAppSubQuery.where(appId);

        Predicate latestAppQuery = cb.equal(modifyTimeRoot, latestAppSubQuery);

        return query
                .where(appRequestStatusPath.in(AppRequestStatus.SUBMITTED), latestAppQuery)
                //.orderBy(buildOrderCriteria(root, cb))
                .getRestriction();

    }

    private List<Order> buildOrderCriteria(Root<AppRequest> root, CriteriaBuilder cb) {
        Path<AppAuditRecord.AppAuditStatus> appAuditStatusPath = root.get("appAuditRecord").get("status");
        Path<Long> lastModifiedTime = root.get("lastUpdateTime");

        Expression<Integer> statusOrderLevel = cb.<Integer>selectCase()
                .when(cb.isNull(appAuditStatusPath), 1)
                .when(cb.equal(appAuditStatusPath, AppAuditRecord.AppAuditStatus.CREATED), 1)
                .when(cb.equal(appAuditStatusPath, AppAuditRecord.AppAuditStatus.APPROVED), 2)
                .when(cb.equal(appAuditStatusPath, AppAuditRecord.AppAuditStatus.REJECTED), 3)
                .otherwise(999);
        return Arrays.asList(cb.asc(statusOrderLevel), cb.desc(lastModifiedTime));
    }