Spring JPA使用CriteriaBuilder動態構造查詢

在使用Spring JPA提供的方法只能進行簡單的CRUD，如果遇到復雜的情況就需要我們動態來構建查詢條件了。這里我們來看使用CriteriaBuilder如何來構造查詢。
核心代碼：

 CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
 CriteriaQuery<Long> query = criteriaBuilder.createQuery(Long.class);
 Root<Order> root = query.from(Order.class);
 query.select(criteriaBuilder.count(root.get("id")));
 Predicate predicate = criteriaBuilder.equal(root.get("id"), 1);
 query.where(predicate);
 Long singleResult = entityManager.createQuery(query).getSingleResult();

1. 調用entityManager.getCriteriaBuilder()來獲取CriteriaBuilder。CriteriaBuilder可以用於創建CriteriaQuery、CriteriaUpdate和CriteriaDelete。除此之外類似count、max等函數也是由CriteriaBuilder來創建的。其中Entitymanager可以使用@PersistenceContext注解來進行注入。
2. 調用criteriaBuilder.createQuery來創建CriteriaQuery。其中createQuery的參數是Query返回值類型。
3. 調用query.from(Order.class)。參數是對應於order表的實體類，query.from類似於sql中的from語句，該方法的執行等價於sql中的from order。
4. 調用 query.select創建映射。 query.select(criteriaBuilder.count(root.get(“id”)))等價於select count(id)。如果執行query.select(root)則等價於select *。
5. 使用CriteriaBuilder構造查詢條件Predicate，該predicate也就是在where后面的條件子句。
6. 將Predicate放在 query.where中。
7. 最后執行查詢獲取數據。

     @Autowired
       EntityManager entityManager;
       @Override
       public TableResultResponse<RiskAnalyzeRecordDto> groupByCreatDateAndDataTime(RiskAnalyzeRecordDto dto, Pageable pageable) {
           CriteriaBuilder cb = entityManager.getCriteriaBuilder();
           CriteriaQuery<Object[]> cq = cb.createQuery(Object[].class);
           Root<RiskAnalyzeRecord> root = cq.from(RiskAnalyzeRecord.class);
           Predicate whereCondition;
           if (dto.getCreatedDateStart()!=null&&dto.getCreatedDateEnd()!=null){
               whereCondition = cb.and(
                       cb.like(root.<String>get("fullId"), dto.getFullId() + "%"),
                       cb.between(root.<Date>get("createdDate"),dto.getCreatedDateStart(),dto.getCreatedDateEnd())
               );
           }else if (dto.getCreatedDateEnd()!=null){
               whereCondition = cb.and(
                       cb.like(root.<String>get("fullId"), dto.getFullId() + "%"),
                       cb.lessThanOrEqualTo(root.<Date>get("createdDate"), dto.getCreatedDateEnd())
               );
           }else if (dto.getCreatedDateStart()!=null){
               whereCondition = cb.and(
                       cb.like(root.<String>get("fullId"), dto.getFullId() + "%"),
                       cb.greaterThanOrEqualTo(root.<Date>get("createdDate"), dto.getCreatedDateStart())
               );
           }else {
               whereCondition = cb.like(root.<String>get("fullId"), dto.getFullId() + "%");
           }
           if (StringUtils.isNotBlank(dto.getDataTime())){
               whereCondition = cb.and(whereCondition,cb.equal(root.get("dataTime"),dto.getDataTime()));
           }
           if (StringUtils.isNotBlank(dto.getRiskId())){
               whereCondition = cb.and(whereCondition,cb.equal(root.get("riskId"),dto.getRiskId()));
           }
           cq.multiselect(root.get("userName"),root.get("createdDate"),root.get("dataTime"), cb.sum(
                       cb.<Integer>selectCase().when(root.<Integer>get("record").isNotNull(), root.<Integer>get("record")).otherwise(0)
            )).where(whereCondition)
            .groupBy(root.get("userName"),root.get("createdDate"),root.get("dataTime")).orderBy(new OrderImpl(root.get("createdDate"),false));
   
           TypedQuery<Object[]> query = entityManager.createQuery(cq);
           query.setFirstResult(pageable.getOffset());
           query.setMaxResults(pageable.getPageSize());
           List<Object[]> list = query.getResultList();
           CriteriaQuery<Long> countQuery = cb.createQuery(Long.class);
           Root<RiskAnalyzeRecord> root1 = countQuery.from(RiskAnalyzeRecord.class);
           countQuery.select(cb.count(root1.get("id"))).
                   where(whereCondition).
                   groupBy(root1.get("userName"),root1.get("createdDate"),root1.get("dataTime"));
           TypedQuery<Long> countTypeQuery = entityManager.createQuery(countQuery);
           int count =  countTypeQuery.getResultList().size();
           List<RiskAnalyzeRecordDto> dtoList = new ArrayList<>();
           for (Object[] object : list) {
               String userName= String.valueOf(object[0]);
               String dataTime= String.valueOf(object[2]);
               Integer record= Integer.valueOf(String.valueOf(object[3]));
               RiskAnalyzeRecordDto elem = new RiskAnalyzeRecordDto();
               elem.setUserName(userName);
               elem.setCreatedDate((Date) object[1]);
               elem.setDataTime(dataTime);
               elem.setRecord(record);
               dtoList.add(elem);
           }
   
           return new TableResultResponse(count, dtoList);
       }

    

   參考文檔：JPA分組查詢，求和，自定義查詢字段，自定義VO承接  Spring JPA使用CriteriaBuilder動態構造查詢