JPA怎么通過Specification實(shí)現(xiàn)復(fù)雜查詢

小編給大家分享一下JPA怎么通過Specification實(shí)現(xiàn)復(fù)雜查詢，希望大家閱讀完這篇文章之后都有所收獲，下面讓我們一起去探討吧！

JPA 通過Specification實(shí)現(xiàn)復(fù)雜查詢

JPA中繼承BaseRepo之后，可以使用最基本的增刪改查，如果想實(shí)現(xiàn)復(fù)雜查詢，則需要借助Specification來完成這個功能：

下面就簡單介紹一下Specification的使用

public void findAll(ConstructPlanPageReqEntity constructPlanPageReqEntity) {
	Integer pageNum = page.getPageNum();
        Integer pageSize = page.getPageSize();
        String costType = constructPlanPageReqEntity.getCostType();
        String name = constructPlanPageReqEntity.getName();
        String planMoneyStart = constructPlanPageReqEntity.getPlanMoneyStart();
        String planMoneyEnd = constructPlanPageReqEntity.getPlanMoneyEnd();
        String singMoneyEnd = constructPlanPageReqEntity.getSingMoneyEnd();
        String signMoneyStart = constructPlanPageReqEntity.getSignMoneyStart();
        long projectId = Long.parseLong(constructPlanPageReqEntity.getProjectId());
        String status = constructPlanPageReqEntity.getStatus();
        //分頁
        pageNum=pageNum-1;
        Pageable pageable = PageRequest.of(pageNum, pageSize);
//多條件匹配查詢
        Specification specification= new Specification<ContractPlanBean>() {
            @Override
            public Predicate toPredicate(Root<ContractPlanBean> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {
                ArrayList<Predicate> list = new ArrayList<>();
                Path<String> costType1 = root.get("costType");
                Path<String> name1 = root.get("name");
                Path<Long> projectId1 = root.get("projectId");
                Path<Object> status1 = root.get("status");
                if (projectId>0){
                    list.add(criteriaBuilder.equal(projectId1,projectId));
                }
                if (StringUtil.isNotEmpty(status)){
                    list.add(criteriaBuilder.equal(status1,status));
                }
                //條件查詢
                if (StringUtil.isNotEmpty(costType)){
                    list.add(criteriaBuilder.equal(costType1,costType));
                }
                //模糊查詢
                if (StringUtil.isNotEmpty(name)){
                    list.add(criteriaBuilder.like(name1,"%"+name+"%"));
                }
                //范圍查詢
                if (StringUtil.isNotEmpty(planMoneyStart)&&StringUtil.isNotEmpty(planMoneyEnd)){
                    try {
                        list.add(criteriaBuilder.between(root.get("planMoney"),NumberUtil.strToDouble(planMoneyStart),NumberUtil.strToDouble(planMoneyEnd)));
                    } catch (Exception e) {
                        throw new ApiException("規(guī)劃金額查詢失敗");
                    }
                }
                 //排序
                criteriaQuery.orderBy(criteriaBuilder.asc(root.get("name")));
                Predicate[] array = new Predicate[list.size()];
                return criteriaBuilder.and(list.toArray(array));
            }
        };
}

以上代碼實(shí)現(xiàn)了多條件查詢，其中需要重寫toPredicate方法，具體參數(shù)：

• 用root.get()獲取bean中的數(shù)據(jù)庫對應(yīng)字段

• 用criteriaBuilder來組建條件查詢語句

上圖是criteriaBuilder各種sql符號的方法名，根據(jù)需求組建不同的sql語句

criteriaBuilder.and(list.toArray(array))這句是最后定義各個sql查詢條件的關(guān)系，這里用的and

至此，復(fù)雜sql語句就拼接完成，本人對Specification的使用未進(jìn)行深入研究，個人覺得相對filter Strem的復(fù)雜查詢來說Specification更繁瑣，因此更傾向于通過Strem的復(fù)雜查詢，這回就不多說了，下次就介紹下如何使用Stream進(jìn)行復(fù)雜查詢

spring-data-jpa Specification拼接復(fù)雜查詢

  public Page<ServiceItem> findAll(Map<String, String[]> params, ServiceItemConsumeStatus serviceItemConsumeStatus,ServiceItemStatus serviceItemStatus, Pageable pageable) {
        return dao.findAll(spec(serviceItemConsumeStatus, serviceItemStatus, params), pageable);
    }
    private Specification<ServiceItem> spec(final ServiceItemConsumeStatus serviceItemConsumeStatus, 
    final ServiceItemStatus serviceItemStatus, Map<String, String[]> params) {
        Collection<SearchFilter> filters = SearchFilter.parse(params).values();
        final Specification<ServiceItem> fsp = SearchFilter.spec(filters, ServiceItem.class);
        Specification<ServiceItem> sp = new Specification<ServiceItem>() {
            public Predicate toPredicate(Root<ServiceItem> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
                Predicate pred = fsp.toPredicate(root, query, cb);
                if (ServiceItemConsumeStatus.可消費(fèi).equals(serviceItemConsumeStatus)) {
                    pred = cb.and(pred, cb.gt(root.get("countLeft").as(int.class), 0));
                } else if (ServiceItemConsumeStatus.消費(fèi)完畢.equals(serviceItemConsumeStatus)) {
                    pred = cb.and(pred, cb.le(root.get("countLeft").as(int.class), 0));
                }
                if (serviceItemStatus != null) {
                    pred = cb.and(pred, cb.equal(root.get("status"), serviceItemStatus));
                }
                return pred;
            }
        };
        return sp;
    }

看完了這篇文章，相信你對“JPA怎么通過Specification實(shí)現(xiàn)復(fù)雜查詢”有了一定的了解，如果想了解更多相關(guān)知識，歡迎關(guān)注億速云行業(yè)資訊頻道，感謝各位的閱讀！