Adding a Login Screen to a Vaadin Application Using Spring Security

In this chapter, you secure the CRM application by setting up Spring Security and adding a login screen to limit access to logged-in users.

Creating a Login View

Start by creating a new view, LoginView, in the views package.

LoginView.java

package com.example.application.views;
import com.vaadin.flow.component.html.H1;
import com.vaadin.flow.component.login.LoginForm;
import com.vaadin.flow.component.orderedlayout.VerticalLayout;
import com.vaadin.flow.router.BeforeEnterEvent;
import com.vaadin.flow.router.BeforeEnterObserver;
import com.vaadin.flow.router.PageTitle;
import com.vaadin.flow.router.Route;
@Route("login") 1
@PageTitle("Login | Vaadin CRM")
public class LoginView extends VerticalLayout implements BeforeEnterObserver {
    private final LoginForm login = new LoginForm(); 2
    public LoginView(){
        addClassName("login-view");
        setSizeFull(); 3
        setAlignItems(Alignment.CENTER);
        setJustifyContentMode(JustifyContentMode.CENTER);
        login.setAction("login"); 4
        add(new H1("Vaadin CRM"), login);
    }
    @Override
    public void beforeEnter(BeforeEnterEvent beforeEnterEvent) {
        // inform the user about an authentication error
        if(beforeEnterEvent.getLocation()  5
        .getQueryParameters()
        .getParameters()
        .containsKey("error")) {
            login.setError(true);
        }
    }
}

1. Map the view to the "login" path. LoginView should take up the whole browser window, so don’t use MainLayout as the parent.

2. Instantiate a LoginForm component to capture username and password.

3. Make LoginView full size and center its content both horizontally and vertically, by calling setAlignItems(Alignment.CENTER) and setJustifyContentMode(JustifyContentMode.CENTER).

4. Set the LoginForm action to "login" to post the login form to Spring Security.

5. Read query parameters and show an error if a login attempt fails.

Build the application and navigate to http://localhost/login. You should see a centered login form.

Setting up Spring Security to Handle Logins

With the login screen in place, you now need to configure Spring Security to perform the authentication and to prevent unauthorized users from accessing views.

Installing Spring Security Dependencies

Add the Spring Security dependency in pom.xml:

pom.xml

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

Check that the dependency is downloaded. If you are unsure, run ./mvnw install from the command line to download the dependency.

Next, disable Spring MVC auto-configuration on the Application class, as this interferes with how Vaadin works and can cause strange reloading behavior.

**Application.class**

@SpringBootApplication(exclude = ErrorMvcAutoConfiguration.class)
@NpmPackage(value = "lumo-css-framework", version = "^4.0.10")
public class Application extends SpringBootServletInitializer {
    ...
}

Configuring Spring Security

Create a new package com.example.application.security for classes related to security.

In the new package, create the following classes using the code detailed below:

• SecurityUtils: utility methods.

• CustomRequestCache: a cache to keep track of unauthenticated requests.

• SecurityConfiguration: Spring Security configuration.

• SecurityService: a service for getting information about the logged-in user and logging them out.

SecurityUtils.java

package com.example.application.security;
import com.vaadin.flow.server.HandlerHelper.RequestType;
import com.vaadin.flow.shared.ApplicationConstants;
import org.springframework.security.authentication.AnonymousAuthenticationToken;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.context.SecurityContextHolder;
import javax.servlet.http.HttpServletRequest;
import java.util.stream.Stream;
public final class SecurityUtils {
    private SecurityUtils() {
        // Util methods only
    }
    static boolean isFrameworkInternalRequest(HttpServletRequest request) { 1
        final String parameterValue = request.getParameter(ApplicationConstants.REQUEST_TYPE_PARAMETER);
        return parameterValue != null
            && Stream.of(RequestType.values())
            .anyMatch(r -> r.getIdentifier().equals(parameterValue));
    }
    static boolean isUserLoggedIn() { 2
        Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
        return authentication != null
            && !(authentication instanceof AnonymousAuthenticationToken)
            && authentication.isAuthenticated();
    }
}

1. isFrameworkInternalRequest() determines if a request is internal to Vaadin.

2. isUserLoggedIn() checks if the current user is logged in.

CustomRequestCache.java

package com.example.application.security;
import org.springframework.security.web.savedrequest.HttpSessionRequestCache;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
class CustomRequestCache extends HttpSessionRequestCache {
    @Override
    public void saveRequest(HttpServletRequest request, HttpServletResponse response) {
        if (!SecurityUtils.isFrameworkInternalRequest(request)) {
            super.saveRequest(request, response); 1
        }
    }
}

1. Saves unauthenticated requests, so that, once the user is logged in, you can redirect them to the page they were trying to access.

SecurityConfig.java

package com.example.application.security;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.builders.WebSecurity;
import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
import org.springframework.security.core.userdetails.User;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.security.provisioning.InMemoryUserDetailsManager;
@EnableWebSecurity
@Configuration
public class SecurityConfig extends WebSecurityConfigurerAdapter {
  private static final String LOGIN_PROCESSING_URL = "/login";
  private static final String LOGIN_FAILURE_URL = "/login?error";
  private static final String LOGIN_URL = "/login";
  private static final String LOGOUT_SUCCESS_URL = "/login";
  /**
   * Require login to access internal pages and configure login form.
   */
  @Override
  protected void configure(HttpSecurity http) throws Exception {
    // Vaadin handles CSRF internally
    http.csrf().disable()
        // Register our CustomRequestCache, which saves unauthorized access attempts, so the user is redirected after login.
        .requestCache().requestCache(new CustomRequestCache())
        // Restrict access to our application.
        .and().authorizeRequests()
        // Allow all Vaadin internal requests.
        .requestMatchers(SecurityUtils::isFrameworkInternalRequest).permitAll()
        // Allow all requests by logged-in users.
        .anyRequest().authenticated()
        // Configure the login page.
        .and().formLogin()
        .loginPage(LOGIN_URL).permitAll()
        .loginProcessingUrl(LOGIN_PROCESSING_URL)
        .failureUrl(LOGIN_FAILURE_URL)
        // Configure logout
        .and().logout().logoutSuccessUrl(LOGOUT_SUCCESS_URL);
  }
  @Bean
  @Override
  public UserDetailsService userDetailsService() {
    UserDetails user = User.withUsername("user")
            .password("{noop}userpass")
            .roles("USER")
            .build();
    return new InMemoryUserDetailsManager(user);
  }
  /**
   * Allows access to static resources, bypassing Spring Security.
   */
  @Override
  public void configure(WebSecurity web) {
    web.ignoring().antMatchers(
        // Client-side JS
        "/VAADIN/**",
        // the standard favicon URI
        "/favicon.ico",
        // the robots exclusion standard
        "/robots.txt",
        // web application manifest
        "/manifest.webmanifest",
        "/sw.js",
        "/offline.html",
        // icons and images
        "/icons/**",
        "/images/**",
        "/styles/**",
        // (development mode) H2 debugging console
        "/h2-console/**");
  }
}

Restricting Access to Vaadin Views

Spring Security restricts access to content based on paths. Vaadin applications are single-page applications. This means that they do not trigger a full browser refresh when you navigate between views, even though the path does change. To secure a Vaadin application, you need to wire Spring Security to the Vaadin navigation system.

To do this, create a new class in the security package, ConfigureUIServiceInitListener.java.

ConfigureUIServiceInitListener.java

package com.example.application.security;
import com.example.application.views.LoginView;
import com.vaadin.flow.component.UI;
import com.vaadin.flow.router.BeforeEnterEvent;
import com.vaadin.flow.server.ServiceInitEvent;
import com.vaadin.flow.server.VaadinServiceInitListener;
import org.springframework.stereotype.Component;
@Component 1
public class ConfigureUIServiceInitListener implements VaadinServiceInitListener {
    @Override
    public void serviceInit(ServiceInitEvent event) { 2
        event.getSource().addUIInitListener(uiEvent -> {
            final UI ui = uiEvent.getUI();
            ui.addBeforeEnterListener(this::authenticateNavigation);
        });
    }
    private void authenticateNavigation(BeforeEnterEvent event) { 3
        if (!LoginView.class.equals(event.getNavigationTarget())
            && !SecurityUtils.isUserLoggedIn()) {
            event.rerouteTo(LoginView.class);
        }
    }
}

1. The @Component annotation registers the listener. Vaadin will pick it up on startup.

2. In serviceInit(), listen for the initialization of the UI (the internal root component in Vaadin) and then add a listener before every view transition.

3. In authenticateNavigation(), reroute all requests to the login, if the user is not logged in.

Finally, create a service for accessing user information and logging out. Create SecurityService.java in the security package.

SecurityService.java

package com.example.application.security;
import com.vaadin.flow.component.UI;
import com.vaadin.flow.server.VaadinServletRequest;
import org.springframework.security.core.context.SecurityContext;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.web.authentication.logout.SecurityContextLogoutHandler;
import org.springframework.stereotype.Component;
@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);
    }
}

Adding a Logout Button

You can now log in to the application. The final thing that is needed is a logout button in the application header.

In MainLayout, add a link to the header:

MainLayout.java

package com.example.application.views;
import com.example.application.security.SecurityService;
import com.example.application.views.list.ListView;
import com.vaadin.flow.component.applayout.AppLayout;
import com.vaadin.flow.component.applayout.DrawerToggle;
import com.vaadin.flow.component.button.Button;
import com.vaadin.flow.component.html.H1;
import com.vaadin.flow.component.orderedlayout.FlexComponent;
import com.vaadin.flow.component.orderedlayout.HorizontalLayout;
import com.vaadin.flow.component.orderedlayout.VerticalLayout;
import com.vaadin.flow.router.HighlightConditions;
import com.vaadin.flow.router.RouterLink;
import com.vaadin.flow.theme.Theme;
@Theme(themeFolder = "flowcrmtutorial")
public class MainLayout extends AppLayout {
    private final SecurityService securityService;
    public MainLayout(SecurityService securityService) { 1
        this.securityService = securityService;
        createHeader();
        createDrawer();
    }
    private void createHeader() {
        H1 logo = new H1("Vaadin CRM");
        logo.addClassNames("text-l", "m-m");
        Button logout = new Button("Log out", e -> securityService.logout()); 2
        HorizontalLayout header = new HorizontalLayout(new DrawerToggle(), logo, logout); 3
        header.setDefaultVerticalComponentAlignment(FlexComponent.Alignment.CENTER);
        header.expand(logo); 4
        header.setWidth("100%");
        header.addClassNames("py-0", "px-m");
        addToNavbar(header);
    }
    private void createDrawer() {
        RouterLink listLink = new RouterLink("List", ListView.class);
        listLink.setHighlightCondition(HighlightConditions.sameLocation());
        addToDrawer(new VerticalLayout(
            listLink,
            new RouterLink("Dashboard", DashboardView.class)
        ));
    }
}

1. Autowire the SecurityService and save it in a field.

2. Create a logout button that calls the logout() method in the service.

3. Add the button to the header layout.

4. Call header.expand(logo) to make the logo take up all the extra space in the layout. This pushes the logout button to the far right.

Stop and restart the server to pick up the new Maven dependencies. You should now be able to log in and out of the app. Verify that you can’t access http://localhost/dashboard without being logged in. You can log in with:

• Username: user

• Password: userpass

You have now built a full-stack CRM application with navigation and authentication. In the next chapter, you’ll learn how to turn it into a PWA to make it installable on mobile and desktop.

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export class RenderBanner extends HTMLElement {
  connectedCallback() {
    this.renderBanner();
  }
  renderBanner() {
    let bannerWrapper = document.getElementById('tocBanner');
    if (bannerWrapper) {
      return;
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    // Add an empty ToC div in case page doesn't have one.
    if (!tocEl) {
      const pageTitle = document.querySelector(
        'main > article > header[class^=PageHeader-module--pageHeader]'
      );
      tocEl = document.createElement('div');
      tocEl.classList.add('toc');
      pageTitle?.insertAdjacentElement('afterend', tocEl);
    }
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    bannerWrapper = document.createElement('div');
    bannerWrapper.id = 'tocBanner';
    tocEl?.appendChild(bannerWrapper);
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    const text = document.querySelector('.toc-banner-source-text')?.innerHTML;
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          <a href='${link}'>
            <div class="toc-banner--img"></div>
            <div class='toc-banner--content'>${text}</div>
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        </div>`;
    bannerWrapper.innerHTML = bannerHtml;
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}