diff --git a/simplesamlphp_auth.install b/simplesamlphp_auth.install
index 05020a6..456dd2c 100644
--- a/simplesamlphp_auth.install
+++ b/simplesamlphp_auth.install
@@ -23,7 +23,7 @@ function simplesamlphp_auth_install() {
   $user_settings->set('register', 'admin_only');
   $user_settings->save();
   // Inform the user about disabling the open registration.
-  drupal_set_message(t('The SimpleSAMLphp Authentication module disabled the user registration. You can manually enable it again in the <a href=":user_settings_url">Account settings</a>.', [
+  \Drupal::messenger()->addMessage(t('The SimpleSAMLphp Authentication module disabled the user registration. You can manually enable it again in the <a href=":user_settings_url">Account settings</a>.', [
     ':user_settings_url' => Url::fromRoute('entity.user.admin_form')->toString(),
   ]), 'warning');
   $config->save();
@@ -64,7 +64,7 @@ function simplesamlphp_auth_requirements($phase) {
         'severity'    => REQUIREMENT_INFO,
         'title'       => 'simpleSAMLphp_auth',
         'value'       => t('SimpleSAMLphp authentication is NOT activated'),
-        'description' => t('It can be activated on the <a href=":config_page">configuration page</a>.', [':config_page' => \Drupal::url('simplesamlphp_auth.admin_settings')]),
+        'description' => t('It can be activated on the <a href=":config_page">configuration page</a>.', [':config_page' => Url::fromRoute('simplesamlphp_auth.admin_settings')->toString()]),
       ];
     }
   }
diff --git a/simplesamlphp_auth.services.yml b/simplesamlphp_auth.services.yml
index d90cadc..43dcc3e 100644
--- a/simplesamlphp_auth.services.yml
+++ b/simplesamlphp_auth.services.yml
@@ -4,7 +4,7 @@ services:
     arguments: ['@config.factory', '@current_user', '@router.admin_context', '@module_handler', '@request_stack', '@messenger']
   simplesamlphp_auth.drupalauth:
     class: Drupal\simplesamlphp_auth\Service\SimplesamlphpDrupalAuth
-    arguments: ['@simplesamlphp_auth.manager', '@config.factory', '@entity_type.manager', '@logger.channel.simplesamlphp_auth', '@externalauth.externalauth', '@current_user']
+    arguments: ['@simplesamlphp_auth.manager', '@config.factory', '@entity_type.manager', '@logger.channel.simplesamlphp_auth', '@externalauth.externalauth', '@current_user', '@messenger', '@module_handler']
   simplesamlphp_auth_event_subscriber:
     class: Drupal\simplesamlphp_auth\EventSubscriber\SimplesamlSubscriber
     arguments: ['@simplesamlphp_auth.manager', '@current_user', '@config.factory', '@logger.channel.simplesamlphp_auth']
diff --git a/src/EventSubscriber/SimplesamlSubscriber.php b/src/EventSubscriber/SimplesamlSubscriber.php
index 3bc47b9..9fef199 100644
--- a/src/EventSubscriber/SimplesamlSubscriber.php
+++ b/src/EventSubscriber/SimplesamlSubscriber.php
@@ -4,6 +4,7 @@ namespace Drupal\simplesamlphp_auth\EventSubscriber;
 
 use Drupal\Core\Config\ConfigFactoryInterface;
 use Drupal\Core\Session\AccountInterface;
+use Drupal\Core\Url;
 use Drupal\simplesamlphp_auth\Service\SimplesamlphpAuthManager;
 use Symfony\Component\HttpFoundation\RedirectResponse;
 use Symfony\Component\HttpKernel\KernelEvents;
@@ -122,7 +123,7 @@ class SimplesamlSubscriber implements EventSubscriberInterface {
     if (\Drupal::currentUser()->isAnonymous() && \Drupal::routeMatch()->getRouteName() == 'user.login') {
 
       // Get the path (default: '/saml_login') from the 'simplesamlphp_auth.saml_login' route.
-      $saml_login_path = \Drupal::url('simplesamlphp_auth.saml_login');
+      $saml_login_path = Url::fromRoute('simplesamlphp_auth.saml_login')->toString();
 
       // Redirect directly to the external IdP.
       $response = new RedirectResponse($saml_login_path, RedirectResponse::HTTP_FOUND);
diff --git a/src/Service/SimplesamlphpDrupalAuth.php b/src/Service/SimplesamlphpDrupalAuth.php
index d8036ab..7481c9b 100644
--- a/src/Service/SimplesamlphpDrupalAuth.php
+++ b/src/Service/SimplesamlphpDrupalAuth.php
@@ -8,6 +8,8 @@ use Drupal\user\UserInterface;
 use Drupal\Core\Session\AccountInterface;
 use Psr\Log\LoggerInterface;
 use Drupal\externalauth\ExternalAuthInterface;
+use Drupal\Core\Messenger\MessengerInterface;
+use Drupal\Core\Extension\ModuleHandlerInterface;
 
 /**
  * Service to link SimpleSAMLphp authentication with Drupal users.
@@ -56,6 +58,20 @@ class SimplesamlphpDrupalAuth {
    */
   protected $currentUser;
 
+  /**
+   * The messenger.
+   *
+   * @var \Drupal\Core\Messenger\MessengerInterface
+   */
+  protected $messenger;
+
+  /**
+   * The module handler service.
+   *
+   * @var \Drupal\Core\Extension\ModuleHandlerInterface
+   */
+  protected $moduleHandler;
+
   /**
    * {@inheritdoc}
    *
@@ -71,14 +87,20 @@ class SimplesamlphpDrupalAuth {
    *   The ExternalAuth service.
    * @param \Drupal\Core\Session\AccountInterface $account
    *   The currently logged in user.
+   * @param \Drupal\Core\Messenger\MessengerInterface $messenger
+   *   The messenger.
+   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
+   *   The module handler service.
    */
-  public function __construct(SimplesamlphpAuthManager $simplesaml_auth, ConfigFactoryInterface $config_factory, EntityTypeManagerInterface $entity_type_manager, LoggerInterface $logger, ExternalAuthInterface $externalauth, AccountInterface $account) {
+  public function __construct(SimplesamlphpAuthManager $simplesaml_auth, ConfigFactoryInterface $config_factory, EntityTypeManagerInterface $entity_type_manager, LoggerInterface $logger, ExternalAuthInterface $externalauth, AccountInterface $account, MessengerInterface $messenger, ModuleHandlerInterface $module_handler) {
     $this->simplesamlAuth = $simplesaml_auth;
     $this->config = $config_factory->get('simplesamlphp_auth.settings');
     $this->entityTypeManager = $entity_type_manager;
     $this->logger = $logger;
     $this->externalauth = $externalauth;
     $this->currentUser = $account;
+    $this->messenger = $messenger;
+    $this->moduleHandler = $module_handler;
   }
 
   /**
@@ -127,7 +149,8 @@ class SimplesamlphpDrupalAuth {
 
       // We're not allowed to register new users on the site through simpleSAML.
       // We let the user know about this and redirect to the user/login page.
-      drupal_set_message(t("We are sorry. While you have successfully authenticated, you are not yet entitled to access this site. Please ask the site administrator to provision access for you."));
+      $this->messenger
+        ->addMessage(t('We are sorry. While you have successfully authenticated, you are not yet entitled to access this site. Please ask the site administrator to provision access for you.'), 'status');
       $this->simplesamlAuth->logout(base_path());
 
       return FALSE;
@@ -157,7 +180,8 @@ class SimplesamlphpDrupalAuth {
         }
         // User is not permitted to login to Drupal via SAML.
         // Log out of SAML and redirect to the front page.
-        drupal_set_message(t('We are sorry, your user account is not SAML enabled.'));
+        $this->messenger
+          ->addMessage(t('We are sorry, your user account is not SAML enabled.'), 'status');
         $this->simplesamlAuth->logout(base_path());
         return FALSE;
       }
@@ -169,8 +193,8 @@ class SimplesamlphpDrupalAuth {
         // Allow other modules to decide if there is an existing Drupal user,
         // based on the supplied SAML atttributes.
         $attributes = $this->simplesamlAuth->getAttributes();
-        foreach (\Drupal::moduleHandler()->getImplementations('simplesamlphp_auth_existing_user') as $module) {
-          $return_value = \Drupal::moduleHandler()->invoke($module, 'simplesamlphp_auth_existing_user', [$attributes]);
+        foreach ($this->moduleHandler->getImplementations('simplesamlphp_auth_existing_user') as $module) {
+          $return_value = $this->moduleHandler->invoke($module, 'simplesamlphp_auth_existing_user', [$attributes]);
           if ($return_value instanceof UserInterface) {
             $account = $return_value;
             if ($this->config->get('debug')) {
@@ -192,7 +216,8 @@ class SimplesamlphpDrupalAuth {
       }
       catch (\Exception $ex) {
         watchdog_exception('simplesamlphp_auth', $ex);
-        drupal_set_message(t('Error registering user: An account with this username already exists.'), 'error');
+        $this->messenger
+          ->addMessage(t('Error registering user: An account with this username already exists.'), 'error');
       }
     }
 
@@ -224,7 +249,7 @@ class SimplesamlphpDrupalAuth {
           if ($this->currentUser->id() != $existing_account->id()) {
             $existing = TRUE;
             $this->logger->critical("Error on synchronizing name attribute for uid %new_uid: an account with the username %username and uid %existing_uid already exists.", ['%username' => $name, '%new_uid' => $this->currentUser->id(), '%existing_uid' => $existing_account->id()]);
-            drupal_set_message(t('Error synchronizing username: an account with this username already exists.'), 'error');
+            $this->messenger->addMessage(t('Error synchronizing username: an account with this username already exists.'), 'error');
           }
         }
 
@@ -234,7 +259,7 @@ class SimplesamlphpDrupalAuth {
       }
       else {
         $this->logger->critical("Error on synchronizing name attribute: no username available for Drupal user %id.", ['%id' => $account->id()]);
-        drupal_set_message(t('Error synchronizing username: no username is provided by SAML.'), 'error');
+        $this->messenger->addMessage(t('Error synchronizing username: no username is provided by SAML.'), 'error');
       }
     }
 
@@ -245,7 +270,7 @@ class SimplesamlphpDrupalAuth {
       }
       else {
         $this->logger->critical("Error on synchronizing mail attribute: no email address available for Drupal user %id.", ['%id' => $account->id()]);
-        drupal_set_message(t('Error synchronizing mail: no email address is provided by SAML.'), 'error');
+        $this->messenger->addMessage(t('Error synchronizing mail: no email address is provided by SAML.'), 'error');
       }
     }
 
@@ -308,7 +333,7 @@ class SimplesamlphpDrupalAuth {
     }
 
     $attributes = $this->simplesamlAuth->getAttributes();
-    \Drupal::modulehandler()->alter('simplesamlphp_auth_user_roles', $roles, $attributes);
+    $this->moduleHandler->alter('simplesamlphp_auth_user_roles', $roles, $attributes);
     return $roles;
   }