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@Controller
public class ArticleController {

    @Autowired
    UserRepository userRepository;
    @Autowired
    ArticleRepositoryImpl articleRepository;
    @Autowired
    CategoryRepository categoryRepository;

    @PostMapping("/finishArticle")
    public String saveArticle(@ModelAttribute("article") Article article, @AuthenticationPrincipal UserDetails userDetails){
        User user = userRepository.findUserByName(userDetails.getUsername());
        article.setWriter(user);
        user.addWrittenArticles(article);
        articleRepository.save(article);
        return "home";
    }

    @PostMapping("/saveArticle")
    public String saveTheArticle(@ModelAttribute("tempArticles") Article article, @AuthenticationPrincipal UserDetails userDetails){
        System.out.println(article);
        /*
        User user = userRepository.findUserByName(userDetails.getUsername());
        Article dbArticle = articleRepository.findById(article.getId());
        dbArticle.addSaver(user);
        articleRepository.save(article);
        */return "home";
    }

    @PostMapping("/search")
    public String showSearchedArticles(@ModelAttribute("tempCategory") Category category, Model model){
        //Category dbCategory = categoryRepository.findByTitle(category.getTi tle());
        System.out.println(category);
        // List<Article> articleList = dbCategory.getArticles();
        //model.addAttribute("articlelist",articleList);
        return "home";
    }
}

@Controller
@RequestMapping("/*{username}")
public class DemoController {

    @Autowired
    private CategoryRepository categoryRepository;
    @Autowired
    private ArticleRepository articleRepository;
    @Autowired
    private UserRepository userRepository;

        @GetMapping()
        public String showHome(Model model){
            List<Category> categories = categoryRepository.findAll();
            Category category = new Category();
            model.addAttribute("category",category);
            model.addAttribute("categories",categories);
            return "home";
        }


    @GetMapping("/write")
    public String showWritingPage(Model model){


        Article article = new Article();
        List<Category> categories = categoryRepository.findAll();
        model.addAttribute("categories",categories);
        model.addAttribute("article", article);
        model.addAttribute("category",article.getCategory());
        model.addAttribute("writer",article.getWriter());
        return "writing-page";

    }

    @GetMapping("/showwritedArticles")
    public String showWritedArticles(Model model, @AuthenticationPrincipal UserDetails userDetails){
        User user = userRepository.findUserByName(userDetails.getUsername());
           List<Article> articles= userRepository.findUserByName(user.getName()).getWrittenArticles();
            model.addAttribute("articles",articles);
            return "writedArticles";
    }

    @GetMapping("/showsavedArticles")
    public String showSavedArticles(@AuthenticationPrincipal UserDetails userDetails, Model model){
        User user = userRepository.findUserByName(userDetails.getUsername());
        model.addAttribute("savedarticles",user.getSavedArticles());
        return"savedArticles";
    }

home.html

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Home</title>
</head>
<body>
  <h2>
    Hi
  </h2>

  <form action="#" th:action="@{/logout}" method="post">
    <input type="submit" value="Logout"/>
  </form>

<a  th:href="@{${#authentication.name}+'/write'}"> MAKALE YAZ</a>
  <br><br>
  <a  th:href="@{${#authentication.name}+'/showwritedArticles'}"> YAZILAN MAKALELER</a>
  <br><br>
MAKALE ARA  <br><br>




<br><br>
  <a th:href="@{${#authentication.name}+'/showsavedArticles'}">KAYDEDİLMİŞ MAKALELER</a>
  <br><br>






<form action="#" th:action="@{/search}" th:object="${category}" method="post">
    <select th:object="${category}">
        <option th:each="tempCategory : ${categories}" th:value="${tempCategory.id}"th:text="${tempCategory.title}"></option>
    </select>
    <input type="submit"value="ARA">
</form>

  


</body>
</html>

writedArticles.html

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Medium Makale Görüntüleme</title>
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css">
    <style>
        body {
            font-family: Arial, sans-serif;
            padding: 20px;
        }
        .container {
            max-width: 800px;
            margin: auto;
        }
        .article {
            margin-bottom: 40px;
        }
        .article-title {
            font-size: 24px;
            font-weight: bold;
            margin-bottom: 10px;
        }
        .article-meta {
            color: #666;
            margin-bottom: 20px;
        }
        .article-content {
            line-height: 1.6;
        }
    </style>
</head>
<body>
<div class="container">
    <!-- Makale bilgileri -->
    <div class="article" th:each="tempArticles : ${articles}">
        <h1 class="article-title" th:text="${tempArticles.title}">Makale Başlığı</h1>
        <p class="article-meta" th:text="${tempArticles.writer}">Yazar - Tarih</p>
        <div class="article-content" th:utext="${tempArticles.text}">
            Makale içeriği buraya gelecek.
        </div>
        <div>
            <form action="#" th:action="@{/saveArticle}" th:object="${tempArticles}" method="post">
                <input type="submit" value="KAYDET">

            </form>
        </div>
    </div>
</div>

</body>
</html>
</body>
</html>

Hi everyone!

I try the search articles by category in home.html category is null on DemoController class

and when i try the save article which one i’ve writeen before in writedArticles.html article is null on ArticleController class?

I don’t know why? Is there anyone can help?

It’s my first question on Stackoverflow so sorry for my mistakes in the question :/

By the way i am beginner in Spring MVC/Boot and Thymeleaf