前端调用这个方法报错：
HTTP Status 406 – Not Acceptable
Type Status Report
Description The target resource does not have a current representation that would be acceptable to the user agent, according to the proactive negotiation header fields received in the request, and the server is unwilling to supply a default representation.
方法使用了@ResponseBody来返回json，然后注解 produces="text/html;charset=UTF-8" 又说返回的是 text/html，互相矛盾，去掉注解 produces="text/html;charset=UTF-8" 就好了。
