Securing Spring Boot Applications

@Route("login")
@PageTitle("Login")
@AnonymousAllowed
public class LoginView extends VerticalLayout implements BeforeEnterObserver {

    private LoginForm login = new LoginForm();

    public LoginView() {
        addClassName("login-view");
        setSizeFull();

        setJustifyContentMode(JustifyContentMode.CENTER);
        setAlignItems(Alignment.CENTER);

        login.setAction("login");

        add(new H1("Test Application"), login);
    }

    @Override
    public void beforeEnter(BeforeEnterEvent beforeEnterEvent) {
        if(beforeEnterEvent.getLocation()
            .getQueryParameters()
            .getParameters()
            .containsKey("error")) {
            login.setError(true);
        }
    }
}

<dependencies>
    <!-- other dependencies -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-security</artifactId>
    </dependency>
    <!-- other dependencies -->
</dependencies>

public class MainLayout extends AppLayout {

    private SecurityService securityService;

    public MainLayout(@Autowired SecurityService securityService) {
        this.securityService = securityService;

        H1 logo = new H1("Vaadin CRM");
        logo.addClassName("logo");
        HorizontalLayout header;
        if (securityService.getAuthenticatedUser() != null) {
            Button logout = new Button("Logout", click ->
                    securityService.logout());
            header = new HorizontalLayout(logo, logout);
        } else {
            header = new HorizontalLayout(logo);
        }

        // Other page components omitted.

        addToNavbar(header);
    }
}

@Component
public class SecurityService {

    private static final String LOGOUT_SUCCESS_URL = "/";

    public UserDetails getAuthenticatedUser() {
        SecurityContext context = SecurityContextHolder.getContext();
        Object principal = context.getAuthentication().getPrincipal();
        if (principal instanceof UserDetails) {
            return (UserDetails) context.getAuthentication().getPrincipal();
        }
        // Anonymous or no authentication.
        return null;
    }

    public void logout() {
        UI.getCurrent().getPage().setLocation(LOGOUT_SUCCESS_URL);
        SecurityContextLogoutHandler logoutHandler = new SecurityContextLogoutHandler();
        logoutHandler.logout(
                VaadinServletRequest.getCurrent().getHttpServletRequest(), null,
                null);
    }
}

@EnableWebSecurity // (1)
@Configuration
public class SecurityConfiguration
                extends VaadinWebSecurity { // (2)

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        // Delegating the responsibility of general configurations
        // of http security to the super class. It's configuring
        // the followings: Vaadin's CSRF protection by ignoring
        // framework's internal requests, default request cache,
        // ignoring public views annotated with @AnonymousAllowed,
        // restricting access to other views/endpoints, and enabling
        // ViewAccessChecker authorization.
        // You can add any possible extra configurations of your own
        // here (the following is just an example):

        // http.rememberMe().alwaysRemember(false);

        // Configure your static resources with public access before calling
        // super.configure(HttpSecurity) as it adds final anyRequest matcher
        http.authorizeRequests().antMatchers("/public/**")
            .permitAll();

        super.configure(http); // (3)

        // This is important to register your login view to the
        // view access checker mechanism:
        setLoginView(http, LoginView.class); // (4)
    }

    @Override
    public void configure(WebSecurity web) throws Exception {
        // Customize your WebSecurity configuration.
        super.configure(web);
    }

    /**
     * Demo UserDetailsManager which only provides two hardcoded
     * in memory users and their roles.
     * NOTE: This shouldn't be used in real world applications.
     */
    @Bean
    public UserDetailsManager userDetailsService() {
        UserDetails user =
                User.withUsername("user")
                        .password("{noop}user")
                        .roles("USER")
                        .build();
        UserDetails admin =
                User.withUsername("admin")
                        .password("{noop}admin")
                        .roles("ADMIN")
                        .build();
        return new InMemoryUserDetailsManager(user, admin);
    }
}

@Route(value = "", layout = MainView.class)
@PageTitle("Public View")
@AnonymousAllowed
public class PublicView extends VerticalLayout {
    // ...
}

@Route(value = "private", layout = MainView.class)
@PageTitle("Private View")
@PermitAll
public class PrivateView extends VerticalLayout {
    // ...
}

@Route(value = "admin", layout = MainView.class)
@PageTitle("Admin View")
@RolesAllowed("ADMIN") // <- Should match one of the user's roles (case-sensitive)
public class AdminView extends VerticalLayout {
    // ...
}

@RolesAllowed("ADMIN")
public abstract class AbstractAdminView extends VerticalLayout {
    // ...
}

@Route(value = "user-listing", layout = MainView.class)
@PageTitle("User Listing")
public class UserListingView extends AbstractAdminView {
    // ...
}