【pageHelper】pageHelper的使用

 　　　　PageHelper.startPage(pageNum, pageSize, sortColumn);
        List<UcUser> list = userMapper.queryUcUserAll();
        PageInfo<UcUser> pageInfo = new PageInfo<>(list);
        return pageInfo;

 /**
     * 分页查询所有用户
     *
     * @param
     */
    @RequestMapping("/queryUserAll")
    @Api
    public void queryUserAll(Integer pageNum, Integer pageSize, String sortColumn) {
        if (pageNum == null || pageSize == null) {
            sendJson(false, "pageNum和pageSize不能为null", "");
            return;
        }
        PageInfo<UcUser> ucUserPageInfo = userService.queryUcUserAll(pageNum, pageSize, sortColumn);
        //判断list是否为空
        if (ObjectUtil.isNull(ucUserPageInfo)) {
            sendJson(false, "", "");
            return;
        }
        sendJson(true, "", ucUserPageInfo);
    }

  public PageInfo<UcUser> queryUcUserAll(Integer pageNum, Integer pageSize ,String sortColumn) {
        //String OrderBy = "createtime DESC";
        PageHelper.startPage(pageNum, pageSize, sortColumn);
        List<UcUser> list = userMapper.queryUcUserAll();
        PageInfo<UcUser> pageInfo = new PageInfo<>(list);
        return pageInfo;
    }