@ApplicationScoped
public class LoginBean
{
    @Inject
    private LoginCredential loginCredential;

    @Inject
    private Identity identity;

    public boolean login(String userName, final String password)
    {
        this.loginCredential.setUserId(userName);
        this.loginCredential.setCredential(new Credential<String>() {
            @Override
            public String getValue()
            {
                return password;
            }
        });

        this.identity.login();
        return this.identity.isLoggedIn();
    }

    public boolean logout()
    {
        this.identity.logout();
        return !this.identity.isLoggedIn();
    }
}

public class CustomBean
{
    @Inject
    private Identity identity;

    @Inject
    private LoginBean loginBean;

    public void execute()
    {
        if(this.loginBean.login("spike", "apache"))
        {
            User user = this.identity.getUser();
            //...
        }
        else
        {
            //...
        }
    }
}