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Chapter 3. JSF web application example

Let's illustrate these ideas with a full example. We're going to implement user login/logout for an application that uses JSF. First, we'll define a request-scoped bean to hold the username and password entered during login, with constraints defined using annotations from the Bean Validation specification:

@Named @RequestScoped

public class Credentials {
    private String username;
    private String password;
    @NotNull @Length(min=3, max=25)
    public String getUsername() { return username; }
    public void setUsername(String username) { this.username = username; }
    @NotNull @Length(min=6, max=20)
    public String getPassword() { return password; }
    public void setPassword(String password) { this.password = password; }

This bean is bound to the login prompt in the following JSF form:


   <h:panelGrid columns="2" rendered="#{!login.loggedIn}">
         <h:outputLabel for="username">Username:</h:outputLabel>
         <h:inputText id="username" value="#{credentials.username}"/>
         <h:outputLabel for="password">Password:</h:outputLabel>
         <h:inputSecret id="password" value="#{credentials.password}"/>
   <h:commandButton value="Login" action="#{login.login}" rendered="#{!login.loggedIn}"/>
   <h:commandButton value="Logout" action="#{login.logout}" rendered="#{login.loggedIn}"/>

Users are represented by a JPA entity:


public class User {
   private @NotNull @Length(min=3, max=25) @Id String username;
   private @NotNull @Length(min=6, max=20) String password;
   public String getUsername() { return username; }
   public void setUsername(String username) { this.username = username; }
   public String setPassword(String password) { this.password = password; }

(Note that we're also going to need a persistence.xml file to configure the JPA persistence unit containing User.)

The actual work is done by a session-scoped bean that maintains information about the currently logged-in user and exposes the User entity to other beans:

@SessionScoped @Named

public class Login implements Serializable {
   @Inject Credentials credentials;
   @Inject @UserDatabase EntityManager userDatabase;
   private User user;
   public void login() {
      List<User> results = userDatabase.createQuery(
         "select u from User u where u.username = :username and u.password = :password")
         .setParameter("username", credentials.getUsername())
         .setParameter("password", credentials.getPassword())
      if (!results.isEmpty()) {
         user = results.get(0);
      else {
         // perhaps add code here to report a failed login
   public void logout() {
      user = null;
   public boolean isLoggedIn() {
      return user != null;
   @Produces @LoggedIn User getCurrentUser() {
      return user;

@LoggedIn and @UserDatabase are custom qualifier annotations:


public @interface LoggedIn {}

public @interface UserDatabase {}

We need an adaptor bean to expose our typesafe EntityManager:

class UserDatabaseProducer {

   @Produces @UserDatabase @PersistenceContext 
   static EntityManager userDatabase;

Now DocumentEditor, or any other bean, can easily inject the current user:

public class DocumentEditor {

   @Inject Document document;
   @Inject @LoggedIn User currentUser;
   @Inject @DocumentDatabase EntityManager docDatabase;
   public void save() {

Or we can reference the current user in a JSF view:

<h:panelGroup rendered="#{login.loggedIn}">
   signed in as #{currentUser.username}

Hopefully, this example gave you a taste of the CDI programming model. In the next chapter, we'll explore dependency injection in greater depth.