controller/ArticleController.java

public class ArticleController {

    private ArticleRepository articleRepository; --- ➋ articleRepository 객체 선언

    (중략)
    @PostMapping("/articles/create")
    public String createArticle(ArticleForm form) {
        System.out.println(form.toString());
        // 1. DTO를 엔티티로 변환
        Article article = form.toEntity(); 
        // 2. 리파지터리로 엔티티를 DB에 저장

        Article saved = articleRepository.save(article); --- ➊  article 엔티티를 저장해 saved 객체에 반환

        return "";
    }
}