Spring Boot Security with Vaadin Login
<p>I try to build an application based on Spring Boot (1.2.7.RELEASE) and Vaadin (7.6.3). My problem is that I'm not able to integrate Spring Security with Vaadin. I want a custom Vaadin built LoginScreen and Spring Security control. My project setup is as follows:</p>

<pre><code>@Configuration
@EnableWebSecurity
public class SpringSecurityConfig extends WebSecurityConfigurerAdapter {

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http.csrf().disable().
                exceptionHandling().authenticationEntryPoint(new LoginUrlAuthenticationEntryPoint("/login")).accessDeniedPage("/accessDenied")
                .and().authorizeRequests()
                .antMatchers("/VAADIN/**", "/PUSH/**", "/UIDL/**", "/login", "/login/**", "/error/**", "/accessDenied/**", "/vaadinServlet/**").permitAll()
                .antMatchers("/authorized", "/**").fullyAuthenticated();
    }
}
</code></pre>

<p>And here is my Vaadin login UI</p>

<pre><code> @SpringUI(path = "/login")
    @Title("LoginPage")
    @Theme("valo")
    public class LoginUI extends UI {

        TextField user;
        PasswordField password;
        Button loginButton = new Button("Login", this::loginButtonClick);
        private static final String username = "username";
        private static final String passwordValue = "test123";

        @Override
        protected void init(VaadinRequest request) {
            setSizeFull();

            user = new TextField("User:");
            user.setWidth("300px");
            user.setRequired(true);
            user.setInputPrompt("Your username");

            password = new PasswordField("Password:");
            password.setWidth("300px");
            password.setRequired(true);
            password.setValue("");
            password.setNullRepresentation("");

            VerticalLayout fields = new VerticalLayout(user, password, loginButton);
            fields.setCaption("Please login to access the application");
            fields.setSpacing(true);
            fields.setMargin(new MarginInfo(true, true, true, false));
            fields.setSizeUndefined();

            VerticalLayout uiLayout = new VerticalLayout(fields);
            uiLayout.setSizeFull();
            uiLayout.setComponentAlignment(fields, Alignment.MIDDLE_CENTER);
            setStyleName(Reindeer.LAYOUT_BLUE);
            setFocusedComponent(user);

            setContent(uiLayout);
        }

        public void loginButtonClick(Button.ClickEvent e) {
           //authorize/authenticate user
           //tell spring that my user is authenticated and dispatch to my mainUI
        }

    }
</code></pre>

<p>When I start my application spring redirects me to my login UI, which is fine. </p>

<p>But I don't know how to authenticate the user against the spring security mechanism and dispatch to my mainUI. </p>

<p>I'm also facing the problem with csrf tokens, if I don't disable csrf I'll get the crfs token is null exception. I found a lot of examples handling those problems but there is no solution provided with Vaadin.</p>

<p>Thanks for help.</p>