java后台接收json数据，报错com.alibaba.fastjson.JSONObject cannot be cast to xxx

　　从前台接收json封装的list数据，在后台接收时一直报错，com.alibaba.fastjson.jsonobject cannot be cast to xxx，

　　使用这种方式接收可以接收

 1 @requestmapping(value = "/insertuser", method = requestmethod.post)
 2 public resultt insertuser(@requestbody map<string,list<user>> map){
 3     list<user> userlist = map.get("insertuserlist");  
 4 }
 5 
 6 //前台json格式
 7 {
 8     "insertuserlist": [
 9         {
10             "firstname": "brett",
11             "lastname": "mclaughlin",
12             "email": "aaaa"
13         },
14         {
15             "firstname": "jason",
16             "lastname": "hunter",
17             "email": "bbbb"
18         },
19         {
20             "firstname": "elliotte",
21             "lastname": "harold",
22             "email": "cccc"
23         }
24     ]
25 }