What happens when you login?

The login page is defined using pure XHTML with JSF controls.
The form uses JSF EL value binding and method binding
expressions to refer to Seam components. For example,
#{user.username}
refers to a property of the
User
entity bean and #{login.login}
refers to a method of the LoginAction
stateless
session bean. Both beans are EJB 3.0 POJOs managed by Seam.
<div>
<h:outputLabel for="username">Login Name</h:outputLabel>
<h:inputText id="username" value="#{user.username}" />
</div>
<div>
<h:outputLabel for="password">Password</h:outputLabel>
<h:inputSecret id="password" value="#{user.password}" />
</div>
... ...
<div class="buttonBox">
<h:commandButton action="#{login.login}"
value="Account Login" class="button" />
</div>
The User
enity bean is mapped to the Seam
context variable named user
bean via the
@Name
annotation. User
is
a session scoped bean, meaning that the user
component value is retained for the entire session for
each user. You might also notice there are validation annotation
on the data properties. We will discuss those annotations in the
next step.
@Entity
@Name("user")
@Scope(SESSION)
public class User implements Serializable {
private String username;
private String password;
private String name;
@NotNull
@Length(min=5, max=15)
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
@Id
@Length(min=5, max=15)
public String getUsername () {
return username;
}
public void setUsername (String username) {
this.username = username;
}
// ... ...
}
LoginAction
is an EJB 3.0 session bean mapped
to the Seam context variable named login
. When
the login button is clicked, the JSF method binding
#{login.login}
is evaluated, and the
login()
method is invoked upon LoginAction
.
@Stateless
@Name("login")
public class LoginAction implements Login
{
@In @Out
private User user;
@PersistenceContext
private EntityManager em;
public String login()
{
List<User> results = em.createQuery("from User where username=:username and password=:password")
.setParameter("username", user.getUsername())
.setParameter("password", user.getPassword())
.getResultList();
if ( results.size()==0 )
{
FacesMessages.instance().add("Invalid login");
return "login";
}
else
{
user = results.get(0);
Contexts.getSessionContext().set("loggedIn", true);
return "main";
}
}
}
The @In
annotation tells Seam to inject a User
when any method of LoginAction
is invoked. The @Out
annotation indicates the LoginAction
bean can change the
value of the user
context variable and make the new instance
available to other session beans and JSF pages.