jpa Specification动态查询分页-实例

作者：LoveEmperor-王子様

1.Specification接口中定义了如下一个方法：

Predicate toPredicate(Root<T> root, CriteriaQuery<?> query, CriteriaBuilder cb);

一、动态查询分页应用代码示例：
controller接口：

    @PostMapping("/xx-xx-xx")
    @Timed
    public Page<InvoiceInfo> getAllInvoiceInfos(@Valid @RequestBody InvoiceListVo vo) throws Exception{
        log.debug("REST request to get all InvoiceInfos");

        return invoiceInfoService.findByCondition(vo);
    }

service方法：

    public Page<InvoiceInfo> findByCondition(InvoiceListVo vo) {
        Pageable pageable = new PageRequest(vo.getPageNumber(), vo.getPageSize(), Sort.Direction.ASC, "id");

        Page<InvoiceInfo> page = this.invoiceInfoRepository.findAll(getCondition(vo), pageable);

        return page;
    }

    private Specification<InvoiceInfo> getCondition(InvoiceListVo vo){
        Specification<InvoiceInfo> sp = new Specification<InvoiceInfo>() {
            /**
             * @param root root参数是我们用来对应实体的信息的。
             * @param query
             * @param cb criteriaBuilder可以帮助我们制作查询信息。
             * @return
             */
            @Override
            public Predicate toPredicate(Root<InvoiceInfo> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
                // 创建 Predicate
                Predicate predicate = cb.conjunction();
                // 组装条件
                if(!vo.getPhone().equals("0")){
//                    predicate.add(cb.equal(root.get("phone"), vo.getPhone()));
                    predicate.getExpressions().add(cb.equal(root.get("phone"), vo.getPhone()));
                }
                if(0 != vo.getTitleType()){
                    predicate.getExpressions().add(cb.equal(root.get("titleType"), vo.getTitleType()));
                }
                if(null != vo.getInvoiceTitle()){
                    predicate.getExpressions().add(cb.equal(root.get("invoiceTitle"), "%"+vo.getInvoiceTitle()+"%"));
                }
                return predicate;
            }

        };
        return sp;
    }

JpaRepository：

@SuppressWarnings("unused")
@Repository
public interface InvoiceInfoRepository extends JpaRepository<InvoiceInfo, Long>,JpaSpecificationExecutor<InvoiceInfo> {
}

二、动态查询不分页：

    public List<InvoiceInfo> findByCondition(InvoiceListVo vo){
        List<InvoiceInfo> resultList = null;
        Specification querySpecifi = new Specification<InvoiceInfo>() {
            @Override
            public Predicate toPredicate(Root<InvoiceInfo> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {

                List<Predicate> predicates = new ArrayList<>();
                if(!vo.getPhone().equals("0")){
                    predicates.add(criteriaBuilder.equal(root.get("phone"), vo.getPhone()));
                }
                if(0 != vo.getTitleType()){
                    predicates.add(criteriaBuilder.equal(root.get("titleType"), vo.getTitleType()));
                }
                if(null != vo.getInvoiceTitle()){
                    predicates.add(criteriaBuilder.equal(root.get("invoiceTitle"), "%"+vo.getInvoiceTitle()+"%"));
                }
                return criteriaBuilder.and(predicates.toArray(new Predicate[predicates.size()]));
            }
        };
        resultList =  this.invoiceInfoRepository.findAll(querySpecifi);
        return resultList;
    }

三、只分页查询：

    @Transactional(readOnly = true)
    public Page<InvoiceInfo> findAll(Integer page,Integer size) {
        Pageable pageable = new PageRequest(page, size, Sort.Direction.ASC, "id");
        return invoiceInfoRepository.findAll(pageable);

    }