https://blog.csdn.net/qq_43061290/article/details/104577391
```
//把保存数据序列化为json数据
ObjectMapper mapper=new ObjectMapper();
String josn = mapper.writeValueAsString(info);
//设置content-Type
response.setContentType("application/json;charset=utf-8");
//把json写到前台页面
response.getWriter().write(josn);
```
直接写给前端不做任何处理
```
ObjectMapper mapper = new ObjectMapper();
response.setContentType("application/json;charset=utf-8");
mapper.writeValue(response.getOutputStream(),info);
```
写给前端之前先把数据封装到session中，一般用于登陆后在前端显示用户名