Ajax异步加载数据及Redis缓存

//categoryListServlet准备分类数据
ProductService service = new ProductService();
List<Category> categoryList = service.findAllCategoryList();
response.setContentType("text/html; charset=utf-8");
Gson gson = new Gson();
String json = gson.toJson(categoryList);
response.getWriter().write(json);

<script type="text/javascript">
          //head.jsp加载完成后，ajax异步加载分类条
          $(function(){
              
              var content= "";
              $.post(
                      "${pageContext.request.contextPath}/categoryList",
                      function(data){
                          //[{"cid":"xxx","cname":"aaa"},{"cid":"xxx","cname":"aaa"}]
                          for(var i=0;i<data.length;i++){
                              content += "<li><a href=‘#‘>"+data[i].cname+"</a></li>";
                          }
                          //将拼接好的类别，写入到页面
                          $("#categoryUI").html(content);  
                      },
                      "json"
              );
              
          });
        
        
        </script>

//查询缓存中有无分类数据，如果没有查询写入缓存
Jedis jedis = JedisPoolUtils.getJedis();
String categoryListJson = jedis.get("categoryListJson");
if(categoryListJson == null){
    System.out.println("缓存没有数据 查询数据库");
    ProductService service = new ProductService();
    List<Category> categoryList = service.findAllCategoryList();
    Gson gson = new Gson();
    categoryListJson = gson.toJson(categoryList);
    jedis.set("categoryListJson", categoryListJson);
}

//准备分类数据    
response.setContentType("text/html; charset=utf-8");
response.getWriter().write(categoryListJson);