springboot的controller返回对象，怎么样前端才能接收到json数据呢？

Question

    @RequestMapping(value="getUserById")
    @ResponseBody
    public User getUserById(int userId){
        System.out.println("userId="+userId);
        return businessService.getUserById(userId);
    }

浏览器调用结果：

Tue Oct 30 13:46:21 CST 2018
There was an unexpected error (type=Internal Server Error, status=500).
No converter found for return value of type: class com.sunlei.springboot.model.User

难道springboot不会做默认的json转换吗？我看maven里面已经导入了jackson的各种包了，还缺什么设置？