How to display menu from database in a JSF template

Question

I want to display menu in JSF template. Every user of my application has different menu and the menu is stored in database. Here is my code,

MenuBean.java

public List<Menuitem> getUserMenu() {
    List<Menuitem> menuitems = (List<Menuitem>) em.createQuery("_____________").setParameter("_______", _______).getResultList();
    return menuitems;
}

pageTemplate.xhtml

<div class="container">
    <div id="navigation">
        <ul>
            <ui:repeat var="_item" value="#{menuitemBean.userMenu}">
                <li><h:outputLink value="#{_item.url}">
                        <h:outputText value="#{_item.name}" />
                    </h:outputLink></li>
            </ui:repeat>
        </ul>
    </div>

    <div id="content">
        <h1>
            <ui:insert name="header" />
        </h1>
        <h2>
            <ui:insert name="subheader" />
        </h2>

        <ui:insert name="main" />
    </div>
</div>

Problem is each time I navigate to a new page (.xhtml file) which is using the same template (pageTemplate.xhtml) the menu is loading all over again.

How can I load the menu only once per user.

score 4 · Answer 1 · answered Jan 29 '13 at 11:27

If the menu is dependent on the user, it would be better to create a bean with a scope session that will store the content of this menu. This way, once the menu is initialized the first time, it will not be re-initialized. Your code will look like that:

public class MySessionBean ... {

    private List<Menuitem> menuItems = null;

    public List<Menuitem> getUserMenu() {
        if (menuItems == null) {
            // Initialize the menu items.
            menuItems = ...;
        }
        return menuitems;
    }

Note that you can also initialize the menuItems objects in the constructor, or in a post-construct method (i.e. a method called just after the bean is instantiated).

An important thing also : do not put database access code in your beans (your em.createQuery(...)). Move that on service / DAO layers, and let the bean call the service to retrieve the information needed to build the menu items.

Thank you, I've added the database access in the method, just to simplify the question posted here. Implemented in the way suggested. — Latte, Jan 29 '13 at 11:48

score 2 · Answer 2 · edited May 23 '17 at 11:51

You should NOT put logic accessing the database in a getter method, because they are often called more than once in the same request.

To load your menu once for each user, put the property in a @SessionScoped backing bean and then initialize it in a @PostConstruct annotated method:

@SessionScoped
public SomeBean {
    private List<Menuitem> menuItems;

    @PostConstruct
    public void init() {
        menuItems = (List<Menuitem>) em.createQuery("_____________")
                           .setParameter("_______", _______).getResultList();
    }
    // getter and setter for menuItems
}

As the bean is in the session scope, it will exist as one instance for each user session in your application.

Note that I assumed you are using JSF 2, because you tagged the question as java-ee-6.

How to display menu from database in a JSF template

2 Answers2