我用ajax不会分页，不知道该怎么写

问题遇到的现象和发生背景

我用ajax来显示列表和做其他操作，因为ajax无法往model和session里存值，所以我在上一页下一页那里取得值就是第一次进去界面时session里的值，他就只能在第一页和第二页之间跳，因为他取得值一直都是1和2，不知道这里该怎么写解决

问题相关代码，请勿粘贴截

//成功后展示列表函数
    function showMedicineList(json) {
        let list = json.data.list;
        var html = "";
        for (var i = 0; i < list.length; i++) {
            html += "<tr>" +
                "<td align= 'center'>" + "<input type='checkbox' name= 'medicineListCheckBox' value =" + list[i].mid + ">" + "</td>" +
                "<td align= 'center' height='80'>" + list[i].mid + "</td>" +
                "<td align= 'center'>" + list[i].mname + "</td>" +
                "<td align= 'center'>" + list[i].mprice + "</td>" +
                "<td align= 'center'>" + list[i].type + "</td>" +
                "<td align='center'>" +
                "<button class= 'btn btn-info' >" + "<a href=/01_ssm_integration_war_exploded/findMedicineByMid/" + list[i].mid + ">" + "<font color='white'>" + "修改" + "</font>" + "</a>" + "</button>"
                + "</td>" +
                "<td align='center'>" +
                "<button id = 'deleteMedicine' class='btn btn-danger' onclick= deleteMedicine(" + list[i].mid + ") >" +
                "<font color='white'>" + "删除" + "</font>" + "</button>" +
                "</td>" +
                "</tr>"
        }
        html += "<td align='center'>" + "共<" + json.data.total + ">条记录" + "</td>"
        html += "<td align='center'>" + "共<" + json.data.pages + ">页" + "</td>"
        html += "<td align='center'>" + "当前第<" + json.data.pageNum + ">页" + "</td>"
        html += "<td>"
        html += "<button onclick='firstPage()'> "  + "首页" + "</button>"
        html += "<button onclick='prePage(${pageNum})'> "  + "上一页" + "</button>"
        html += "<button onclick='nextPage(${pageNum},${pages})'> "  + "下一页" + "</button>"
        html += "<button onclick='lastPage(${pages})'> "  + "尾页" + "</button>"
        html += "</td>"
        $("#testBody").html(html);
    }

@RequestMapping("/medicineList")
    @ResponseBody
    public JsonResult<PageInfo> medicineList(@RequestParam(defaultValue = "1",value = "pageNum") Integer pageNum){
        PageHelper.startPage(pageNum,5);
        List<Medicine> data = medicineService.findMedicineList();
        PageInfo<Medicine> pageInfo = new PageInfo<>(data);
        session.setAttribute("pages",pageInfo.getPages());
        System.out.println(pageNum);
        session.setAttribute("pageNum",pageInfo.getPageNum());
        return new JsonResult<>(200,pageInfo);
    }

运行结果及报错内容

我的解答思路和尝试过的方法

我想要达到的结果

你干嘛不用 elementUI的table来实现呢列表都不用你这样去写超简单的