Many to one. How to associate one object with another?

Question

I have 2 entities User and Article

User

@Entity
@Table(name = "user")
public class User {
    @Id
    @GeneratedValue
    @Column(name="user_id")
    private Integer id;

    @Column(name="name")
    private String name;

    @OneToMany(mappedBy = "userId")
    private List<Article> articles;

Article

@Entity
@Table(name = "article")
public class Article {
    @Id
    @GeneratedValue
    private Integer articleId;

    private String name;

    @ManyToOne
    @JoinColumn(name = "user_id")
    private User userId;

I can register a user then go to his page and from there go to a page that has a form for submitting an article.

<form:form method="POST" modelAttribute="article"
        action="${pageContext.request.contextPath}/addArticle">
        <table>
            <tbody>
                <tr>
                    <td>Title:</td>
                    <td><form:input path="name"></form:input></td>
                </tr>
                <tr>
                    <td>Author id:</td>
                    <td><form:input path="userId"></form:input></td> 
                </tr>
<%--                <form:input type="text" path="userId" disabled="true"/> --%>
<%--                    <form:input type="hidden" path="id" id="id"/> --%>
                <tr>
                    <td><input value="Add" type="submit"></td>
                    <td></td>
                </tr>
            </tbody>
        </table>
    </form:form>

The problem is, I don't know how to associate the article with that user. For now my ArticleController looks like this

ArticleController

@Controller
public class ArticleController {

    @Autowired
    private ArticleService articleService;

    @Autowired
    private UserService userService;

    @RequestMapping(value = "/addArticle/{id}", method = RequestMethod.GET)
    public String addArticle(@PathVariable Integer id, Model model){
        User user = userService.getUserById(id);
        Article article = new Article();
        model.addAttribute("user", user);
        model.addAttribute("article", article);
        return "addArticle";
    }

    @RequestMapping(value = "/addArticle", method = RequestMethod.POST)
    public ModelAndView addArticle(@ModelAttribute Article article) {

        ModelAndView mav = new ModelAndView();
        articleService.addArticle(article);
        mav.setViewName("redirect:/success");
        return mav;
    }
}

How do I make it so

<form:input path="userId" disabled="true"></form:input>

will hold the value of user id? Do I even need to pass there an id or does it have to be an user object?

What do I have to change in this method?

public ModelAndView addArticle

I'm using mysql and spring data jpa

@Alan I deleted that part, but the problem wasn't really there. Thanks for the link anyway. — gjin, Oct 06 '16 at 07:56

score 1 · Accepted Answer · answered Oct 06 '16 at 08:55

I would remove the path="userId" because you only enter the id and don't pass an actual object and replace it with name

<form:input name="userId"></form:input>

You can then add HttpServletRequest request as additional parameter to your addArticle class

 public ModelAndView addArticle(HttpServletRequest request, @ModelAttribute Article article) {

This should allow you to access the userid from your form and retrive the user

User user = userService.getUserById(id);

Then you have to set the User

Article article = new Article();
article.setUser(user)

Many to one. How to associate one object with another?

1 Answers1