Sanzhar Zhanibekov

Изменил
spring.jpa.hibernate.ddl-auto=create
на
spring.jpa.hibernate.ddl-auto=update

Нужно было использовать ModelAndView

@GetMapping("/fill-blank")
    public ModelAndView getRequest(@RequestParam(name = "course", required = false, defaultValue = "1") String idCourse, ModelMap model) {
        List<Course> courses = courseDao.getCourses();
        List<CourseDto> courseDtoList = new ArrayList<>();
        for (Course course : courses) {
            if (course.getId() == Integer.parseInt(idCourse))
                courseDtoList.add(convertToDto(course));
        }
        for (Course course : courses) {
            if (course.getId() != Integer.parseInt(idCourse))
                courseDtoList.add(convertToDto(course));
        }

        model.addAttribute("courseCard", courseDtoList);

        return new ModelAndView("/request_course", model);
    }
<code>