APiGen Notifications

Multi-channel notification delivery system with template management, delivery tracking, user preferences, real-time WebSocket delivery, and robust retry logic.

🎯 Features

• 5 Notification Channels: Email, SMS, Push (Mobile), In-App, Webhook
• Multi-Provider Support: SendGrid, Mailgun, AWS SES (Email) | Twilio, AWS SNS (SMS) | FCM, APNs (Push)
• 4 Template Engines: Thymeleaf, Mustache, FreeMarker, Simple variable substitution
• User Preferences: Per-channel, category-based, quiet hours with timezone support
• Delivery Tracking: Full lifecycle tracking with engagement metrics (opens, clicks)
• Bulk Sending: Parallel batch processing with configurable delay
• Real-Time WebSocket: Push notifications to connected clients
• Retry Logic: Exponential backoff with configurable strategies
• Rate Limiting: Per-channel and global limits
• Async Operations: Non-blocking with CompletableFuture
• Multi-Locale: Template support for multiple languages

🚀 Quick Start

1. Configuration

apigen:
  notifications:
    enabled: true
    default-from-email: noreply@example.com
    default-from-name: "My App"
    
    # Email Provider
    email:
      provider: sendgrid  # Options: sendgrid, ses, mailgun
      sendgrid:
        api-key: ${SENDGRID_API_KEY}
    
    # SMS Provider
    sms:
      provider: twilio    # Options: twilio, sns
      twilio:
        account-sid: ${TWILIO_ACCOUNT_SID}
        auth-token: ${TWILIO_AUTH_TOKEN}
        from-number: "+1234567890"
    
    # Push Notifications
    push:
      fcm:
        enabled: true
        credentials-path: /path/to/firebase-credentials.json
      apns:
        enabled: false
    
    # Template Engine
    template:
      engine: thymeleaf  # Options: thymeleaf, mustache, freemarker, simple
      path: classpath:/templates/notifications/
      cache-enabled: true
      cache-ttl: 5m
    
    # Tracking
    tracking:
      enabled: true
      track-opens: true
      track-clicks: true

2. Send Your First Notification

@Service
public class WelcomeService {
    private final NotificationService notificationService;
    
    public void sendWelcomeEmail(User user) {
        NotificationRequest request = NotificationRequest.builder()
            .channel(NotificationChannel.EMAIL)
            .recipient(user.getEmail())
            .subject("Welcome to Our Platform!")
            .templateName("welcome")
            .templateData(Map.of(
                "userName", user.getName(),
                "verificationLink", generateVerificationLink(user)
            ))
            .priority(NotificationPriority.HIGH)
            .build();
        
        // Async send
        notificationService.sendAsync(request)
            .thenAccept(result -> {
                if (result.isSuccess()) {
                    log.info("Welcome email sent: {}", result.getNotificationId());
                } else {
                    log.error("Failed to send: {}", result.getError());
                }
            });
    }
}

📢 Notification Channels

Email Providers

Provider	Features	Use Case
SendGrid	High deliverability, analytics, templates	Marketing + Transactional
Mailgun	Developer-friendly, routing, webhooks	Transactional
AWS SES	Low cost, AWS integration, bounce handling	High volume

SMS Providers

Provider	Features	Coverage
Twilio	Global reach, programmable messaging, delivery reports	Worldwide
AWS SNS	AWS integration, cost-effective, pub/sub	Worldwide

Push Providers

Provider	Platform	Features
FCM (Firebase Cloud Messaging)	Android + iOS	Topics, device groups, analytics
APNs (Apple Push Notification Service)	iOS only	Silent pushes, rich media

📊 Delivery Tracking

Track Engagement

// Track email opens
trackingService.trackEvent(notificationId, DeliveryEvent.OPENED, Instant.now());

// Track link clicks
trackingService.trackEvent(notificationId, DeliveryEvent.CLICKED, 
    Instant.now(), Map.of("linkUrl", "https://..."));

// Track unsubscribes
trackingService.trackEvent(notificationId, DeliveryEvent.UNSUBSCRIBED, Instant.now());

⚡ Real-Time WebSocket Delivery

Client Connection

// JavaScript client
const ws = new WebSocket('ws://localhost:8080/ws/notifications?userId=user_123');

ws.onopen = () => {
    console.log('Connected to notification stream');
    
    // Send ping to keep alive
    setInterval(() => {
        ws.send(JSON.stringify({ type: 'PING' }));
    }, 30000);
};

ws.onmessage = (event) => {
    const message = JSON.parse(event.data);
    
    switch (message.type) {
        case 'NOTIFICATION':
            showNotification(message.payload);
            break;
        case 'UNREAD_COUNT':
            updateBadge(message.payload.count);
            break;
        case 'PONG':
            console.log('Server alive');
            break;
    }
};