步骤 25: 通过各种途径发布通知

留言本应用程序收集了关于会议的反馈。但在给予用户反馈方面，我们做得还不够好。

因为评论需要经过后台审核，用户很可能会不理解它们为什么没有立刻发布。用户甚至会认为出了技术故障而重新提交评论。在提交评论后给予用户反馈，这样就好很多了。

同理，当评论发布时，我们很可能也应该告知用户。我们向他们要了邮箱，所以最好可以利用这个信息。

通知用户的方式有很多。邮件可能是你想到的第一个媒介，但 web 应用内的通知也是一个。甚至我们可以考虑发送手机短信，以及在 Slack 或 Telegram 上发消息。我们有很多选项。

Symfony 的 Notifier 组件实现了很多通知策略：

$ symfony composer req notifier

在浏览器中发送 web 应用的通知

作为第一步，当用户提交评论后，我们在浏览器里直接通知他们评论会经过审核：

patch_file

--- a/src/Controller/ConferenceController.php
+++ b/src/Controller/ConferenceController.php
@@ -14,6 +14,8 @@ use Symfony\Component\HttpFoundation\File\Exception\FileException;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\Messenger\MessageBusInterface;
+use Symfony\Component\Notifier\Notification\Notification;
+use Symfony\Component\Notifier\NotifierInterface;
 use Symfony\Component\Routing\Annotation\Route;
 use Twig\Environment;
@@ -53,7 +55,7 @@ class ConferenceController extends AbstractController
     }
     #[Route('/conference/{slug}', name: 'conference')]
-    public function show(Request $request, Conference $conference, CommentRepository $commentRepository, string $photoDir): Response
+    public function show(Request $request, Conference $conference, CommentRepository $commentRepository, NotifierInterface $notifier, string $photoDir): Response
     {
         $comment = new Comment();
         $form = $this->createForm(CommentFormType::class, $comment);
@@ -82,9 +84,15 @@ class ConferenceController extends AbstractController
             $this->bus->dispatch(new CommentMessage($comment->getId(), $context));
+            $notifier->send(new Notification('Thank you for the feedback; your comment will be posted after moderation.', ['browser']));
+
             return $this->redirectToRoute('conference', ['slug' => $conference->getSlug()]);
         }
+        if ($form->isSubmitted()) {
+            $notifier->send(new Notification('Can you check your submission? There are some problems with it.', ['browser']));
+        }
+
         $offset = max(0, $request->query->getInt('offset', 0));
         $paginator = $commentRepository->getCommentPaginator($conference, $offset);

通知器会用一个 通道 来 发送 一个 通知 给 接收者。

一个通知有一个标题，一个可选的内容，还有一个重要级。

通知会根据它的重要级在一个或多个通道上发送。比如，你可以用手机短信发送紧急通知，用邮件发送常规通知。

对于浏览器内的通知，我们没有接收者。

浏览器内的通知在 通知 段内使用了 flash 消息。我们要更新会议的模板来展示它们：

patch_file

--- a/templates/conference/show.html.twig
+++ b/templates/conference/show.html.twig
@@ -3,6 +3,13 @@
 {% block title %}Conference Guestbook - {{ conference }}{% endblock %}
 {% block body %}
+    {% for message in app.flashes('notification') %}
+        <div class="alert alert-info alert-dismissible fade show">
+            {{ message }}
+            <button type="button" class="close" data-dismiss="alert" aria-label="Close"><span aria-hidden="true">&times;</span></button>
+        </div>
+    {% endfor %}
+
     <h2 class="mb-5">
         {{ conference }} Conference
     </h2>

现在用户会收到通知，知道他们提交的评论会被审核：

一个附加的好处是，当表单出现错误时，我们在网站顶部也会有一个漂亮的通知信息。

小技巧

flash消息使用 HTTP 会话 系统来作为存储媒介。这样带来的后果是 HTTP 缓存无法使用了，因为必须开启会话系统来检查消息。

这也是为什么我们把消息的代码段放在了 show.html.twig 模板而不是主模板里，不然的话首页里的 HTTP 缓存就不可用了。

用邮件通知管理员

之前我们是通过 MailerInterface 接口来发邮件给管理员，通知他有人提交了评论，现在我们改为在消息处理器中使用 Notifier 组件：

patch_file

--- a/src/MessageHandler/CommentMessageHandler.php
+++ b/src/MessageHandler/CommentMessageHandler.php
@@ -4,14 +4,14 @@ namespace App\MessageHandler;
 use App\ImageOptimizer;
 use App\Message\CommentMessage;
+use App\Notification\CommentReviewNotification;
 use App\Repository\CommentRepository;
 use App\SpamChecker;
 use Doctrine\ORM\EntityManagerInterface;
 use Psr\Log\LoggerInterface;
-use Symfony\Bridge\Twig\Mime\NotificationEmail;
-use Symfony\Component\Mailer\MailerInterface;
 use Symfony\Component\Messenger\Handler\MessageHandlerInterface;
 use Symfony\Component\Messenger\MessageBusInterface;
+use Symfony\Component\Notifier\NotifierInterface;
 use Symfony\Component\Workflow\WorkflowInterface;
 class CommentMessageHandler implements MessageHandlerInterface
@@ -21,22 +21,20 @@ class CommentMessageHandler implements MessageHandlerInterface
     private $commentRepository;
     private $bus;
     private $workflow;
-    private $mailer;
+    private $notifier;
     private $imageOptimizer;
-    private $adminEmail;
     private $photoDir;
     private $logger;
-    public function __construct(EntityManagerInterface $entityManager, SpamChecker $spamChecker, CommentRepository $commentRepository, MessageBusInterface $bus, WorkflowInterface $commentStateMachine, MailerInterface $mailer, ImageOptimizer $imageOptimizer, string $adminEmail, string $photoDir, LoggerInterface $logger = null)
+    public function __construct(EntityManagerInterface $entityManager, SpamChecker $spamChecker, CommentRepository $commentRepository, MessageBusInterface $bus, WorkflowInterface $commentStateMachine, NotifierInterface $notifier, ImageOptimizer $imageOptimizer, string $photoDir, LoggerInterface $logger = null)
     {
         $this->entityManager = $entityManager;
         $this->spamChecker = $spamChecker;
         $this->commentRepository = $commentRepository;
         $this->bus = $bus;
         $this->workflow = $commentStateMachine;
-        $this->mailer = $mailer;
+        $this->notifier = $notifier;
         $this->imageOptimizer = $imageOptimizer;
-        $this->adminEmail = $adminEmail;
         $this->photoDir = $photoDir;
         $this->logger = $logger;
     }
@@ -62,13 +60,7 @@ class CommentMessageHandler implements MessageHandlerInterface
             $this->bus->dispatch($message);
         } elseif ($this->workflow->can($comment, 'publish') || $this->workflow->can($comment, 'publish_ham')) {
-            $this->mailer->send((new NotificationEmail())
-                ->subject('New comment posted')
-                ->htmlTemplate('emails/comment_notification.html.twig')
-                ->from($this->adminEmail)
-                ->to($this->adminEmail)
-                ->context(['comment' => $comment])
-            );
+            $this->notifier->send(new CommentReviewNotification($comment), ...$this->notifier->getAdminRecipients());
         } elseif ($this->workflow->can($comment, 'optimize')) {
             if ($comment->getPhotoFilename()) {
                 $this->imageOptimizer->resize($this->photoDir.'/'.$comment->getPhotoFilename());

getAdminRecipients() 方法会返回通知器配置信息里的管理员接收者邮箱；现在来加入你自己的邮箱：

patch_file

--- a/config/packages/notifier.yaml
+++ b/config/packages/notifier.yaml
@@ -13,4 +13,4 @@ framework:
             medium: ['email']
             low: ['email']
         admin_recipients:
-            - { email: [email protected] }
+            - { email: "%env(string:default:default_admin_email:ADMIN_EMAIL)%" }

现在创建 CommentReviewNotification 类：

src/Notification/CommentReviewNotification.php

namespace App\Notification;
use App\Entity\Comment;
use Symfony\Component\Notifier\Message\EmailMessage;
use Symfony\Component\Notifier\Notification\EmailNotificationInterface;
use Symfony\Component\Notifier\Notification\Notification;
use Symfony\Component\Notifier\Recipient\EmailRecipientInterface;
class CommentReviewNotification extends Notification implements EmailNotificationInterface
{
    private $comment;
    public function __construct(Comment $comment)
    {
        $this->comment = $comment;
        parent::__construct('New comment posted');
    }
    public function asEmailMessage(EmailRecipientInterface $recipient, string $transport = null): ?EmailMessage
    {
        $message = EmailMessage::fromNotification($this, $recipient, $transport);
        $message->getMessage()
            ->htmlTemplate('emails/comment_notification.html.twig')
            ->context(['comment' => $this->comment])
        ;
        return $message;
    }
}

EmailNotificationInterface 接口的 asEmailMessage() 方法是可选的，但它可以用来定制邮件。

使用消息通知器而非直接使用 mailer 来发送邮件的好处之一，就是它把通知和通知用到的“通道”解耦了。正如你能看到的，代码中没有地方显式地指出通知应该由邮件发送。

通道其实是根据通知的 重要级 （默认是 low）在 config/packages/notifier.yaml 中配置的。

config/packages/notifier.yaml

framework:
notifier:
    channel_policy:
        # use chat/slack, chat/telegram, sms/twilio or sms/nexmo
        urgent: ['email']
        high: ['email']
        medium: ['email']
        low: ['email']

我们讨论了 browser 和 email 通道。我们再来看看几个更好玩的通道。

和管理员聊天

说实话，我们都在等待积极的反馈，至少是建设性的反馈。如果有人提交的评论里有“很不错”或“很棒”这样的词，我们可能想要比其它评论更快地接受它们。

对于这样的消息，除了常规的邮件通知，我们也想要在类似 Slack 或 Telegram 这样的即时通信系统中收到通知。

为 Symfony 的消息通知器安装 Slack 支持：

$ symfony composer req slack-notifier

作为第一步，用 Slack 访问令牌以及你要发送消息的 Slack 通道的标识来拼接 Slack 的 DSN：slack://ACCESS_TOKEN@default?channel=CHANNEL。

由于访问令牌是敏感信息，要把 Slack 的 DSN 存储在机密存储中：

$ symfony console secrets:set SLACK_DSN

在生产环境中也是一样：

$ APP_ENV=prod symfony console secrets:set SLACK_DSN

启用 Chatter Slack 支持：

patch_file

--- a/config/packages/notifier.yaml
+++ b/config/packages/notifier.yaml
@@ -1,7 +1,7 @@
 framework:
     notifier:
-        #chatter_transports:
-        #    slack: '%env(SLACK_DSN)%'
+        chatter_transports:
+            slack: '%env(SLACK_DSN)%'
         #    telegram: '%env(TELEGRAM_DSN)%'
         #texter_transports:
         #    twilio: '%env(TWILIO_DSN)%'

更新 Notification 类，根据评论的文本内容把它发送到不同的通道（一个简单的正则表达式就能胜任）：

patch_file

--- a/src/Notification/CommentReviewNotification.php
+++ b/src/Notification/CommentReviewNotification.php
@@ -7,6 +7,7 @@ use Symfony\Component\Notifier\Message\EmailMessage;
 use Symfony\Component\Notifier\Notification\EmailNotificationInterface;
 use Symfony\Component\Notifier\Notification\Notification;
 use Symfony\Component\Notifier\Recipient\EmailRecipientInterface;
+use Symfony\Component\Notifier\Recipient\RecipientInterface;
 class CommentReviewNotification extends Notification implements EmailNotificationInterface
 {
@@ -29,4 +30,15 @@ class CommentReviewNotification extends Notification implements EmailNotificatio
         return $message;
     }
+
+    public function getChannels(RecipientInterface $recipient): array
+    {
+        if (preg_match('{\b(great|awesome)\b}i', $this->comment->getText())) {
+            return ['email', 'chat/slack'];
+        }
+
+        $this->importance(Notification::IMPORTANCE_LOW);
+
+        return ['email'];
+    }
 }

由于这稍微调整了邮件的设计，我们也改变了“常规”评论的重要级。

完成！提交一个内容包含 “awesome” 这个词的评论，你应该会在 Slack 里收到一个消息。

在邮件里，你可以实现 ChatNotificationInterface 接口来覆盖 Slack 消息的默认渲染：

patch_file

--- a/src/Notification/CommentReviewNotification.php
+++ b/src/Notification/CommentReviewNotification.php
@@ -3,13 +3,18 @@
 namespace App\Notification;
 use App\Entity\Comment;
+use Symfony\Component\Notifier\Bridge\Slack\Block\SlackDividerBlock;
+use Symfony\Component\Notifier\Bridge\Slack\Block\SlackSectionBlock;
+use Symfony\Component\Notifier\Bridge\Slack\SlackOptions;
+use Symfony\Component\Notifier\Message\ChatMessage;
 use Symfony\Component\Notifier\Message\EmailMessage;
+use Symfony\Component\Notifier\Notification\ChatNotificationInterface;
 use Symfony\Component\Notifier\Notification\EmailNotificationInterface;
 use Symfony\Component\Notifier\Notification\Notification;
 use Symfony\Component\Notifier\Recipient\EmailRecipientInterface;
 use Symfony\Component\Notifier\Recipient\RecipientInterface;
-class CommentReviewNotification extends Notification implements EmailNotificationInterface
+class CommentReviewNotification extends Notification implements EmailNotificationInterface, ChatNotificationInterface
 {
     private $comment;
@@ -31,6 +36,28 @@ class CommentReviewNotification extends Notification implements EmailNotificatio
         return $message;
     }
+    public function asChatMessage(RecipientInterface $recipient, string $transport = null): ?ChatMessage
+    {
+        if ('slack' !== $transport) {
+            return null;
+        }
+
+        $message = ChatMessage::fromNotification($this, $recipient, $transport);
+        $message->subject($this->getSubject());
+        $message->options((new SlackOptions())
+            ->iconEmoji('tada')
+            ->iconUrl('https://guestbook.example.com')
+            ->username('Guestbook')
+            ->block((new SlackSectionBlock())->text($this->getSubject()))
+            ->block(new SlackDividerBlock())
+            ->block((new SlackSectionBlock())
+                ->text(sprintf('%s (%s) says: %s', $this->comment->getAuthor(), $this->comment->getEmail(), $this->comment->getText()))
+            )
+        );
+
+        return $message;
+    }
+
     public function getChannels(RecipientInterface $recipient): array
     {
         if (preg_match('{\b(great|awesome)\b}i', $this->comment->getText())) {

现在好多了，但我们再更进一步。如果可以直接在 Slack 里接受或拒绝一个评论，那岂不是太棒了？

更新通知，让它接受评审 URL，再在 Slack 消息里增加两个按钮：

patch_file

--- a/src/Notification/CommentReviewNotification.php
+++ b/src/Notification/CommentReviewNotification.php
@@ -3,6 +3,7 @@
 namespace App\Notification;
 use App\Entity\Comment;
+use Symfony\Component\Notifier\Bridge\Slack\Block\SlackActionsBlock;
 use Symfony\Component\Notifier\Bridge\Slack\Block\SlackDividerBlock;
 use Symfony\Component\Notifier\Bridge\Slack\Block\SlackSectionBlock;
 use Symfony\Component\Notifier\Bridge\Slack\SlackOptions;
@@ -17,10 +18,12 @@ use Symfony\Component\Notifier\Recipient\RecipientInterface;
 class CommentReviewNotification extends Notification implements EmailNotificationInterface, ChatNotificationInterface
 {
     private $comment;
+    private $reviewUrl;
-    public function __construct(Comment $comment)
+    public function __construct(Comment $comment, string $reviewUrl)
     {
         $this->comment = $comment;
+        $this->reviewUrl = $reviewUrl;
         parent::__construct('New comment posted');
     }
@@ -53,6 +56,10 @@ class CommentReviewNotification extends Notification implements EmailNotificatio
             ->block((new SlackSectionBlock())
                 ->text(sprintf('%s (%s) says: %s', $this->comment->getAuthor(), $this->comment->getEmail(), $this->comment->getText()))
             )
+            ->block((new SlackActionsBlock())
+                ->button('Accept', $this->reviewUrl, 'primary')
+                ->button('Reject', $this->reviewUrl.'?reject=1', 'danger')
+            )
         );
         return $message;

现在就是来反向跟踪改变了。首先，更新消息处理器来通过评审 URL：

patch_file

--- a/src/MessageHandler/CommentMessageHandler.php
+++ b/src/MessageHandler/CommentMessageHandler.php
@@ -60,7 +60,8 @@ class CommentMessageHandler implements MessageHandlerInterface
             $this->bus->dispatch($message);
         } elseif ($this->workflow->can($comment, 'publish') || $this->workflow->can($comment, 'publish_ham')) {
-            $this->notifier->send(new CommentReviewNotification($comment), ...$this->notifier->getAdminRecipients());
+            $notification = new CommentReviewNotification($comment, $message->getReviewUrl());
+            $this->notifier->send($notification, ...$this->notifier->getAdminRecipients());
         } elseif ($this->workflow->can($comment, 'optimize')) {
             if ($comment->getPhotoFilename()) {
                 $this->imageOptimizer->resize($this->photoDir.'/'.$comment->getPhotoFilename());

正如你看到的那样，评审 URL 应该是评论消息的一部分，我们现在来加上它：

patch_file

--- a/src/Message/CommentMessage.php
+++ b/src/Message/CommentMessage.php
@@ -5,14 +5,21 @@ namespace App\Message;
 class CommentMessage
 {
     private $id;
+    private $reviewUrl;
     private $context;
-    public function __construct(int $id, array $context = [])
+    public function __construct(int $id, string $reviewUrl, array $context = [])
     {
         $this->id = $id;
+        $this->reviewUrl = $reviewUrl;
         $this->context = $context;
     }
+    public function getReviewUrl(): string
+    {
+        return $this->reviewUrl;
+    }
+
     public function getId(): int
     {
         return $this->id;

最后，更新控制器，让它生成评审 URL，然后把它传递给评论消息的构造函数：

patch_file

--- a/src/Controller/AdminController.php
+++ b/src/Controller/AdminController.php
@@ -12,6 +12,7 @@ use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\HttpKernel\KernelInterface;
 use Symfony\Component\Messenger\MessageBusInterface;
 use Symfony\Component\Routing\Annotation\Route;
+use Symfony\Component\Routing\Generator\UrlGeneratorInterface;
 use Symfony\Component\Workflow\Registry;
 use Twig\Environment;
@@ -47,7 +48,8 @@ class AdminController extends AbstractController
         $this->entityManager->flush();
         if ($accepted) {
-            $this->bus->dispatch(new CommentMessage($comment->getId()));
+            $reviewUrl = $this->generateUrl('review_comment', ['id' => $comment->getId()], UrlGeneratorInterface::ABSOLUTE_URL);
+            $this->bus->dispatch(new CommentMessage($comment->getId(), $reviewUrl));
         }
         return $this->render('admin/review.html.twig', [
--- a/src/Controller/ConferenceController.php
+++ b/src/Controller/ConferenceController.php
@@ -17,6 +17,7 @@ use Symfony\Component\Messenger\MessageBusInterface;
 use Symfony\Component\Notifier\Notification\Notification;
 use Symfony\Component\Notifier\NotifierInterface;
 use Symfony\Component\Routing\Annotation\Route;
+use Symfony\Component\Routing\Generator\UrlGeneratorInterface;
 use Twig\Environment;
 class ConferenceController extends AbstractController
@@ -82,7 +83,8 @@ class ConferenceController extends AbstractController
                 'permalink' => $request->getUri(),
             ];
-            $this->bus->dispatch(new CommentMessage($comment->getId(), $context));
+            $reviewUrl = $this->generateUrl('review_comment', ['id' => $comment->getId()], UrlGeneratorInterface::ABSOLUTE_URL);
+            $this->bus->dispatch(new CommentMessage($comment->getId(), $reviewUrl, $context));
             $notifier->send(new Notification('Thank you for the feedback; your comment will be posted after moderation.', ['browser']));

解耦代码意味着在多个地方进行改动，但它让测试、理解和重用变得更容易。

再试一次，现在消息的处理已经很完善了：

全面使用异步

我来解释下我们需要去解决的一个小问题。对于每个评论我们都会收到一封邮件和一个 Slack 消息。如果 Slack 消息出错了（错误的通道 id、错误的令牌等等），messenger 发出的消息会在丢弃前重试 3 次。但由于邮件先发出，所以我们会收到 3 封邮件，却没有任何 Slack 消息。解决该问题的一个方案就是像邮件一样异步发送 Slack 消息：

patch_file

--- a/config/packages/messenger.yaml
+++ b/config/packages/messenger.yaml
@@ -20,3 +20,5 @@ framework:
             # Route your messages to the transports
             App\Message\CommentMessage: async
             Symfony\Component\Mailer\Messenger\SendEmailMessage: async
+            Symfony\Component\Notifier\Message\ChatMessage: async
+            Symfony\Component\Notifier\Message\SmsMessage: async

当一切变为异步时，消息就互相独立了。考虑到你可能会想要通过手机接收通知，我们也启用了手机短信的异步发送。

用邮件通知用户

最后一个任务是当评论通过审核后通知用户。你自己来实现这个功能，怎么样？

深入学习

• Symfony 的 flash 消息。

This work, including the code samples, is licensed under a Creative Commons BY-NC-SA 4.0 license.