控制层方法不加@ResponseBody返回的json的方法：

1、使用@ResponseBody表示直接在response中加入一实体(如Json格式)并直接返回
    @RequestMapping(value = "/{courseId}",method = RequestMethod.GET)
    public @ResponseBody Course getCourseInJson(@PathVariable Integer courseId) {
        Course course = courseService.getCoursebyId(courseId);
        return course;
    }

2、返回Json格式数据方法2：
    @RequestMapping(value = "/jsonType/{courseId}",method = RequestMethod.GET)
    public ResponseEntity<Course> getCourseInJson2(@PathVariable Integer courseId) {
        Course course = courseService.getCoursebyId(courseId);
        return new ResponseEntity<>(course, HttpStatus.OK);
    }