在SSM项目中以JSON格式将数据返回给前端，前端该怎么接收和渲染

问题相关代码，请勿粘贴截图

controller

 @RequestMapping("/findByUserId")
    @ResponseBody
    public String findByUserId(int id) throws JsonProcessingException {
        ObjectMapper mapper = new ObjectMapper();
        List<Complain> list = new ArrayList<Complain>();
        list = complainService.findByUserId(id);
        return mapper.writeValueAsString(list);
    }

前端

<script>
        $(function (){
            $("#btn").click(function (){
                $.post("${pageContext.request.contextPath}/complain/findByUserId?id=${sessionScope.user.id}",function (data){
                    var str = "";
                    for (let i =0;i<data.length;i++){
                        str+="<tr>"+
                            "<td>"+data[i].id+"</td>"+
                            "<td>"+data[i].complain_content+"</td>"+
                            "<td>"+data[i].creat_time+"</td>"+
                            // "<td>"+data[i].user.name+"</td>"+
                            // "<td>"+data[i].user.phone+"</td>"+
                            "<td>"+data[i].state+"</td>"+
                            "<td>"+data[i].admin+"</td>"+
                            "<td>"+data[i].reply_time+"</td>"+
                            "<td><a href=/complain/deleteById?id=data[i].id>删除</a></td>"+
                            "</tr>"
                    }
                    $("#show_tbody").html(str)
                })
            })
        })
    </script>