jpa簡單查詢，and、or與分頁排序的使用

傳入分頁參數pageable，和業務參數userId，查詢用戶id爲空，創建時間爲最近一個月的數據或用戶id爲userId的數據。

    @Override
    public Page<PushMessageDTO> findMessage(Pageable pageable,String userId) throws Exception {
        Page<PushMessage> page = PushMessageRepository.findAll(new Specification<PushMessage>() {
            @Override
            public Predicate toPredicate(Root<PushMessage> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder cb) {
                // 新發布制度標準的時間範圍
                SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
                String begin = dateFormat.format(new Date());
                Calendar cl = Calendar.getInstance();
                cl.add(Calendar.MONTH, -1);            //一個月
                String end = dateFormat.format(cl.getTime());
                
                Path<Object> p_time = root.get("createTime");
                Path<Object> p_user = root.get("userId");
                
                Predicate p1 = cb.and(cb.isNull(p_user),cb.lessThanOrEqualTo(p_time.as(String.class), begin),cb.greaterThanOrEqualTo(p_time.as(String.class), end));
                Predicate p = cb.or(p1,cb.equal(p_user, userId));
                
                return p;
            }
        }, new PageRequest(pageable.getPageNumber()-1, pageable.getPageSize(),Sort.Direction.DESC,"createTime"));
        
        return page.map(new Converter<PushMessage, PushMessageDTO>() {
            @Override
            public PushMessageDTO convert(PushMessage PushMessage) {
                PushMessageDTO PushMessageDTO = new PushMessageDTO();
                BeanUtils.copyProperties(PushMessage, PushMessageDTO);
                return PushMessageDTO;
            }
        });
    }