NotifyHub

One API. Every channel.
Unified notification library for Java and Spring Boot.

Website · Documentation · Getting Started

Stop writing different code for each notification channel. NotifyHub gives you a single fluent API to send notifications via Email, SMS, WhatsApp, Slack, Telegram, Discord, Microsoft Teams, Firebase Push, Webhooks, WebSocket, Google Chat, Twitter/X, LinkedIn, Notion, Twitch, YouTube, Instagram, SendGrid, TikTok Shop, Facebook, AWS SNS, Mailgun, PagerDuty — or any custom channel you create.

notify.to(user)
    .via(EMAIL)
    .fallback(SMS)
    .priority(Priority.HIGH)
    .subject("Order confirmed")
    .template("order-confirmed")
    .param("orderId", order.getId())
    .attach(invoicePdf)
    .send();

Why NotifyHub?

	Problem	Without NotifyHub	With NotifyHub
	Email	JavaMail config, MIME types, Session...	`.via(EMAIL)`
📱	SMS	Twilio SDK, different API entirely	`.via(SMS)`
	WhatsApp	Another Twilio setup, prefix logic	`.via(WHATSAPP)`
	Slack	Webhook HTTP, JSON payload	`.via(SLACK)`
	Telegram	Bot API, HTTP client setup	`.via(TELEGRAM)`
	Discord	Webhook HTTP, JSON payload	`.via(DISCORD)`
👥	Teams	Incoming Webhook, MessageCard JSON	`.via(TEAMS)`
	Push	Firebase Admin SDK, credentials...	`.via(PUSH)`
🔗	Webhook	Custom HTTP, payload template	`.via(Channel.custom("pagerduty"))`
	WebSocket	Java WebSocket API, reconnect logic	`.via(WEBSOCKET)`
	Google Chat	Webhook HTTP, JSON payload	`.via(GOOGLE_CHAT)`
	Twitter/X	OAuth 1.0a, API v2 setup	`.via(TWITTER)`
💼	LinkedIn	OAuth 2.0, REST API setup	`.via(LINKEDIN)`
	Notion	Integration Token, API setup	`.via(NOTION)`
	Twitch	OAuth 2.0, Twitch API setup	`.via(TWITCH)`
	YouTube	YouTube Data API v3 setup	`.via(YOUTUBE)`
	Instagram	Meta Graph API setup	`.via(INSTAGRAM)`
📧	SendGrid	SendGrid API, webhook tracking	`.via(Channel.custom("sendgrid"))`
	TikTok Shop	HMAC-SHA256, Shop API	`.via(TIKTOK_SHOP)`
	Facebook	Graph API, Page tokens	`.via(FACEBOOK)`
☁️	AWS SNS	AWS SDK, credentials, ARN	`.via(Channel.custom("aws-sns"))`
	Mailgun	Mailgun API, domain setup	`.via(Channel.custom("mailgun"))`
	PagerDuty	Events API v2, routing key	`.via(Channel.custom("pagerduty"))`
	Multiple channels	Completely different code for each	Same fluent API
Fallback	Manual try/catch chain	`.fallback(SMS)`
Retry	Implement yourself	Built-in exponential backoff
Async	Thread pools, CompletableFuture	`.sendAsync()`
Scheduling	ScheduledExecutor, timer logic	`.schedule(Duration.ofMinutes(30))`
Templates	Each channel has its own engine	One template, all channels
i18n	Manual locale resolution	`.locale(Locale.PT_BR)`
Rate limiting	Token bucket from scratch	Config-driven per-channel
Tracking	Build your own delivery log	Built-in receipts + JPA
Dead letters	Lost in the void	Auto-captured in DLQ
Deduplication	Track sent messages yourself	Built-in content hash / explicit key
Template versions	Manage files manually	`.templateVersion("v2")` + A/B test
Batch	Loop and pray	`.toAll(users).send()`
Monitoring	Wire Micrometer yourself	Auto-configured counters
Health checks	Write an Actuator indicator	Auto-configured
Admin UI	Build your own dashboard	Built-in `/notify-admin`
Circuit breaker	Implement yourself per channel	Built-in per-channel circuit breaker
Orchestration	Manual escalation logic	`.orchestrate().first(EMAIL).ifNoOpen(24h).then(PUSH)`
A/B testing	External service + glue code	Built-in `.abTest("exp").variant(...).split(50,50)`
Testing	Mock everything	`TestNotifyHub` captures all sends
New channel	Build from scratch	Implement one interface

Quick Start
Features
Supported Channels
Admin Dashboard
Spring Boot Integration
Configuration Reference
Without Spring Boot
MCP Server (AI Agents)
Running the Demo
Architecture
Maven Central
Roadmap
License

Quick Start

1. Add the dependency

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-spring-boot-starter</artifactId>
    <version>1.0.0</version>
</dependency>

Need extra channels? Add optional modules:

<!-- SMS + WhatsApp (Twilio) -->
<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-sms</artifactId>
    <version>1.0.0</version>
</dependency>

<!-- Slack / Telegram / Discord / Teams / Firebase Push / Webhook -->
<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-slack</artifactId>
    <version>1.0.0</version>
</dependency>

<!-- WebSocket / Google Chat -->
<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-websocket</artifactId>
    <version>1.0.0</version>
</dependency>

2. Configure in `application.yml`

notify:
  channels:
    email:
      host: smtp.gmail.com
      port: 587
      username: ${GMAIL_USER}
      password: ${GMAIL_PASS}
      from: noreply@myapp.com
      from-name: MyApp
      tls: true
  retry:
    max-attempts: 3
    strategy: exponential
  tracking:
    enabled: true

3. Inject and use

@Service
public class OrderService {

    private final NotifyHub notify;

    public OrderService(NotifyHub notify) {
        this.notify = notify;
    }

    public void confirmOrder(Order order) {
        notify.to(order.getCustomer())
            .via(Channel.EMAIL)
            .subject("Order confirmed!")
            .template("order-confirmed")
            .param("customerName", order.getCustomer().getName())
            .param("orderId", order.getId())
            .param("total", order.getTotal())
            .send();
    }
}

That's it. Three steps.

Features

Fallback Chain

If the primary channel fails, automatically try the next one:

notify.to(user)
    .via(Channel.WHATSAPP)
    .fallback(Channel.SMS)
    .fallback(Channel.EMAIL)
    .template("payment-reminder")
    .param("amount", "R$ 150,00")
    .send();
// Tries WhatsApp -> SMS -> Email

Multi-Channel Send

Send through ALL channels simultaneously:

notify.to(user)
    .via(Channel.EMAIL)
    .via(Channel.SLACK)
    .via(Channel.TEAMS)
    .subject("Security Alert")
    .content("Login from a new device detected")
    .sendAll();

Async Sending

Send notifications without blocking:

// Fire and forget
notify.to(user)
    .via(Channel.EMAIL)
    .template("welcome")
    .sendAsync();

// Or wait for result
CompletableFuture<Void> future = notify.to(user)
    .via(Channel.EMAIL)
    .via(Channel.SLACK)
    .content("Deploy complete!")
    .sendAllAsync();

future.thenRun(() -> log.info("All notifications sent!"));

Retry with Backoff

Automatic retry with exponential or fixed backoff:

# application.yml (global)
notify:
  retry:
    max-attempts: 3
    strategy: exponential  # waits 1s, 2s, 4s...

// Or per-notification
notify.to(user)
    .via(Channel.EMAIL)
    .retry(3)
    .template("invoice")
    .send();

Templates (Mustache)

Create templates in src/main/resources/templates/notify/:

order-confirmed.html (auto-used for email):

<h1>Hello, {{customerName}}!</h1>
<p>Your order <strong>#{{orderId}}</strong> has been confirmed.</p>
<p>Total: <strong>{{total}}</strong></p>

order-confirmed.txt (auto-used for SMS/WhatsApp/Slack/Telegram/Discord/Teams):

Hello {{customerName}}, your order #{{orderId}} is confirmed. Total: {{total}}

The library picks .html for email and .txt for other channels automatically.

i18n (Internationalization)

Templates support locale-based resolution with automatic fallback:

// User with locale
notify.to(user)
    .via(Channel.EMAIL)
    .locale(Locale.forLanguageTag("pt-BR"))
    .template("welcome")
    .param("name", user.getName())
    .send();

Template resolution order: welcome_pt_BR.html -> welcome_pt.html -> welcome.html

Your Notifiable can also return a locale:

public class User implements Notifiable {
    @Override
    public Locale getLocale() {
        return Locale.forLanguageTag("pt-BR");
    }
}

Attachments

Attach files to email notifications:

notify.to(user)
    .via(Channel.EMAIL)
    .subject("Your Invoice")
    .template("invoice")
    .attach("invoice.pdf", pdfBytes, "application/pdf")
    .attach(new File("/reports/monthly.xlsx"))
    .attach(Attachment.fromFile(contractFile))
    .send();

Priority Levels

Set notification priority. URGENT notifications bypass rate limiting:

notify.to(user)
    .via(Channel.EMAIL)
    .priority(Priority.URGENT)
    .subject("SERVER DOWN!")
    .content("Production server is unresponsive")
    .send();

Available priorities: URGENT (bypasses rate limits), HIGH, NORMAL (default), LOW.

Rate Limiting

Control notification throughput per-channel:

notify:
  rate-limit:
    enabled: true
    max-requests: 100
    window: 1m
    channels:
      email:
        max-requests: 50
        window: 1m
      sms:
        max-requests: 10
        window: 1m

Rate limiting uses a token bucket algorithm. URGENT priority notifications always bypass rate limits.

Dead Letter Queue (DLQ)

Failed notifications (after all retries) are automatically captured in the DLQ:

notify:
  tracking:
    enabled: true
    dlq-enabled: true

View and manage dead letters via the admin dashboard at /notify-admin/dlq, or programmatically:

DeadLetterQueue dlq = hub.getDeadLetterQueue();
List<DeadLetter> failed = dlq.findAll();
dlq.remove(deadLetterId); // after manual reprocessing

Batch Send

Send notifications to multiple recipients at once:

// By email addresses
notify.toAll(List.of("user1@test.com", "user2@test.com", "user3@test.com"))
    .via(Channel.EMAIL)
    .subject("System Maintenance")
    .template("maintenance-notice")
    .param("date", "2025-03-01")
    .send();

// By Notifiable entities
notify.toAllNotifiable(users)
    .via(Channel.EMAIL)
    .template("newsletter")
    .send();

// Async batch
notify.toAll(recipients)
    .via(Channel.EMAIL)
    .template("promo")
    .sendAsync();

Delivery Tracking

Track every notification with delivery receipts:

notify:
  tracking:
    enabled: true
    type: memory  # or "jpa" for database persistence

// Send and get a receipt
DeliveryReceipt receipt = notify.to(user)
    .via(Channel.EMAIL)
    .content("Hello!")
    .sendTracked();

System.out.println(receipt.getStatus());    // SENT
System.out.println(receipt.getId());         // uuid
System.out.println(receipt.getTimestamp());  // 2025-01-15T10:30:00Z

For database persistence, add the JPA tracker module:

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-tracker-jpa</artifactId>
    <version>1.0.0</version>
</dependency>

notify:
  tracking:
    enabled: true
    type: jpa

Scheduled Notifications

Schedule notifications for future delivery:

ScheduledNotification scheduled = notify.to(user)
    .via(Channel.EMAIL)
    .subject("Reminder")
    .content("Don't forget your appointment tomorrow!")
    .schedule(Duration.ofHours(24));

// Check status
scheduled.getStatus();        // SCHEDULED, SENT, FAILED, CANCELLED
scheduled.getRemainingDelay(); // PT23H59M...

// Cancel if needed
scheduled.cancel();

Notification Routing

Auto-route notifications based on user preferences:

public class User implements Notifiable {
    @Override
    public List<Channel> getPreferredChannels() {
        return List.of(Channel.WHATSAPP, Channel.SMS, Channel.EMAIL);
    }
}

// Auto-routes: WhatsApp (primary) -> SMS (fallback) -> Email (fallback)
notify.notify(user)
    .template("order-update")
    .param("orderId", "12345")
    .send();

Conditional routing with rules:

NotificationRouter router = NotificationRouter.builder()
    .rule(RoutingRule.timeBasedRule(
        LocalTime.of(9, 0), LocalTime.of(18, 0),
        Channel.SLACK, Channel.EMAIL))  // Slack during business hours, email after
    .build();

Notifiable Interface

Make your User entity a notification recipient:

@Entity
public class User implements Notifiable {

    private String name;
    private String email;
    private String phone;

    @Override
    public String getNotifyEmail() { return email; }

    @Override
    public String getNotifyPhone() { return phone; }

    @Override
    public String getNotifyName() { return name; }

    @Override
    public Locale getLocale() { return Locale.forLanguageTag("pt-BR"); }

    @Override
    public List<Channel> getPreferredChannels() {
        return List.of(Channel.EMAIL, Channel.SMS);
    }
}

Then just pass the user object:

notify.to(user)       // resolves email/phone automatically
    .via(Channel.EMAIL)
    .template("welcome")
    .send();

Or use raw addresses:

notify.to("user@email.com").via(Channel.EMAIL).content("Hello!").send();
notify.toPhone("+5511999999999").via(Channel.SMS).content("Code: 1234").send();

Message Deduplication

Prevent duplicate notifications automatically with content hashing or explicit keys:

notify:
  deduplication:
    enabled: true
    ttl: 24h
    strategy: content-hash  # content-hash | explicit-key | both

// Auto-dedup by content hash (same recipient + channel + content = skipped)
notify.to(user).via(EMAIL).content("Order confirmed").send();
notify.to(user).via(EMAIL).content("Order confirmed").send(); // skipped!

// Dedup by explicit key
notify.to(user).via(EMAIL)
    .deduplicationKey("order-" + orderId)
    .template("order-confirmed")
    .send();

Strategies:

content-hash — SHA-256 hash of recipient + channel + subject + content
explicit-key — uses the key provided via .deduplicationKey("...")
both — uses explicit key if provided, otherwise falls back to content hash

Without Spring Boot:

NotifyHub notify = NotifyHub.builder()
    .deduplicationStore(new InMemoryDeduplicationStore(Duration.ofHours(12)))
    .channel(emailChannel)
    .build();

Template Versioning

Manage multiple versions of templates for A/B testing or gradual rollouts:

templates/notify/
├── order-confirmed.html           ← default version
├── order-confirmed@v1.html        ← version v1
├── order-confirmed@v2.html        ← version v2
├── order-confirmed_pt_BR@v2.html  ← v2 with i18n
└── order-confirmed.txt            ← text default

// Use a specific version
notify.to(user).via(EMAIL)
    .template("order-confirmed")
    .templateVersion("v2")
    .param("orderId", "123")
    .send();

// No version = default template (backward compatible)
notify.to(user).via(EMAIL)
    .template("order-confirmed")
    .send();

// A/B testing
String version = abTestService.getVariant(user, "email-template");
notify.to(user).via(EMAIL)
    .template("welcome")
    .templateVersion(version)  // "v1" or "v2"
    .send();

Resolution order: {name}@{version}_{locale}.{variant} → {name}@{version}.{variant} → {name}_{locale}.{variant} → {name}.{variant}

Custom Channels

Create your own channel by implementing one interface:

@Component
public class PushChannel implements NotificationChannel {

    @Override
    public String getName() { return "push"; }

    @Override
    public void send(Notification notification) {
        firebaseClient.send(notification.getRecipient(), notification.getRenderedContent());
    }

    @Override
    public boolean isAvailable() { return true; }
}

Use it:

notify.to(user)
    .via(Channel.custom("push"))
    .template("new-message")
    .send();

Spring Boot auto-discovers any NotificationChannel bean. No extra config needed.

Event Listeners + Spring Events

Monitor notification outcomes with the listener interface:

@Component
public class NotifyMonitor implements NotificationListener {

    @Override
    public void onSuccess(String channel, String template) {
        metrics.increment("notifications.sent." + channel);
    }

    @Override
    public void onFailure(String channel, String template, Exception error) {
        log.error("Failed on {}: {}", channel, error.getMessage());
        alertService.warn("Channel " + channel + " is failing");
    }

    @Override
    public void onScheduled(String channel, String recipient, Duration delay) {
        log.info("Scheduled for {} in {}", recipient, delay);
    }
}

Or use Spring Application Events (auto-configured):

@Component
public class NotificationEventHandler {

    @EventListener
    public void onSent(NotificationSentEvent event) {
        log.info("Sent via {} to {}", event.getChannel(), event.getRecipient());
    }

    @EventListener
    public void onFailed(NotificationFailedEvent event) {
        log.error("Failed: {}", event.getError().getMessage());
    }
}

Named Recipients

Send notifications to multiple destinations per channel using named aliases. Instead of one hardcoded webhook URL or chat ID, configure as many as you need:

Configure in application.yml:

notify:
  channels:
    discord:
      webhook-url: ${DISCORD_DEFAULT}      # default destination
      username: NotifyHub
      avatar-url: https://example.com/logo.png
      recipients:
        alerts: https://discord.com/api/webhooks/111/aaa
        devops: https://discord.com/api/webhooks/222/bbb
        general: https://discord.com/api/webhooks/333/ccc

    slack:
      webhook-url: ${SLACK_DEFAULT}
      recipients:
        engineering: https://hooks.slack.com/services/XXX/YYY/ZZZ
        marketing: https://hooks.slack.com/services/AAA/BBB/CCC

    telegram:
      bot-token: ${TELEGRAM_BOT_TOKEN}
      chat-id: ${TELEGRAM_DEFAULT_CHAT}
      recipients:
        alerts: "-1001234567890"
        devops: "-1009876543210"

Use with the Java API:

// Send to a named alias
notify.to("alerts").via(DISCORD).content("Server is down!").send();
notify.to("engineering").via(SLACK).content("Deploy complete").send();
notify.to("devops").via(TELEGRAM).content("CPU at 95%").send();

// Send to default (no alias)
notify.to("user").via(DISCORD).content("Hello!").send();

// Pass a raw URL directly (no alias needed)
notify.to("https://discord.com/api/webhooks/444/ddd").via(DISCORD).content("Direct!").send();

Use with the MCP Server (AI Agents):

send_discord(recipient="alerts", body="Server is down!")
send_slack(recipient="engineering", body="Deploy complete")
send_telegram(recipient="devops", body="CPU at 95%")

Environment variables for MCP/Docker:

# Default webhook
NOTIFY_CHANNELS_DISCORD_WEBHOOK_URL=https://discord.com/api/webhooks/111/aaa

# Named recipients (RECIPIENTS_<NAME>)
NOTIFY_CHANNELS_DISCORD_RECIPIENTS_ALERTS=https://discord.com/api/webhooks/222/bbb
NOTIFY_CHANNELS_DISCORD_RECIPIENTS_DEVOPS=https://discord.com/api/webhooks/333/ccc

# Same pattern for all channels
NOTIFY_CHANNELS_SLACK_RECIPIENTS_ENGINEERING=https://hooks.slack.com/services/XXX
NOTIFY_CHANNELS_TELEGRAM_RECIPIENTS_ALERTS=-1001234567890
NOTIFY_CHANNELS_TEAMS_RECIPIENTS_GENERAL=https://outlook.office.com/webhook/XXX
NOTIFY_CHANNELS_GOOGLE_CHAT_RECIPIENTS_TEAM=https://chat.googleapis.com/v1/spaces/XXX

Resolution order: alias match in recipients map > raw URL/value passthrough > default from config.

Supported on: Discord, Slack, Telegram, Teams, Google Chat.

Message Queue (RabbitMQ / Kafka)

Decouple notification sending with async message queues. NotifyHub provides two modules:

RabbitMQ

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-queue-rabbitmq</artifactId>
    <version>1.0.0</version>
</dependency>

spring.rabbitmq.host: localhost
spring.rabbitmq.port: 5672

notify.queue.rabbitmq:
  enabled: true
  queue-name: notifyhub-notifications
  exchange-name: notifyhub-exchange
  routing-key: notification
  consumer:
    enabled: true
    concurrency: 1
    max-concurrency: 5

@Autowired RabbitNotificationProducer producer;

// Enqueue for async delivery
producer.enqueue(QueuedNotification.builder()
    .recipient("user@example.com")
    .channelName("email")
    .subject("Welcome!")
    .templateName("welcome")
    .params(Map.of("name", "Gabriel"))
    .build());
// Consumer picks it up and sends via NotifyHub automatically

Apache Kafka

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-queue-kafka</artifactId>
    <version>1.0.0</version>
</dependency>

spring.kafka.bootstrap-servers: localhost:9092

notify.queue.kafka:
  enabled: true
  topic: notifyhub-notifications
  consumer:
    enabled: true
    group-id: notifyhub-group
    concurrency: 1

@Autowired KafkaNotificationProducer producer;

// Same API as RabbitMQ — just different transport
producer.enqueue(QueuedNotification.builder()
    .recipient("+5548999999999")
    .channelName("sms")
    .rawContent("Your code is 1234")
    .priority("URGENT")
    .build());

Both modules support: templates, priority, deduplication keys, delivery tracking, and phone number routing for SMS/WhatsApp.

Circuit Breaker

Per-channel circuit breaker prevents cascading failures. If a channel fails repeatedly, the circuit opens and short-circuits further attempts:

// Without Spring Boot
NotifyHub notify = NotifyHub.builder()
    .channel(emailChannel)
    .circuitBreaker(CircuitBreakerConfig.defaults()) // 5 failures → open for 30s
    .build();

// Custom thresholds
NotifyHub notify = NotifyHub.builder()
    .channel(emailChannel)
    .circuitBreaker(CircuitBreakerConfig.custom()
        .failureThreshold(3)
        .openDuration(Duration.ofMinutes(1))
        .windowSize(Duration.ofSeconds(30))
        .build())
    .build();

# Spring Boot
notify:
  circuit-breaker:
    enabled: true
    failure-threshold: 5
    open-duration: 30s
    window-size: 60s

States: CLOSED (normal) → OPEN (rejecting) → HALF_OPEN (testing recovery). The health endpoint includes circuit breaker status per channel.

Bulkhead (Concurrency Isolation)

Limit concurrent sends per channel to prevent resource exhaustion:

NotifyHub notify = NotifyHub.builder()
    .channel(emailChannel)
    .bulkhead(BulkheadConfig.defaults())       // 10 concurrent per channel
    .bulkhead(BulkheadConfig.perChannel(5))    // or custom limit
    .build();

Multi-Channel Orchestration

Build escalation workflows that promote through channels if the user doesn't engage:

notify.to(user)
    .orchestrate()
    .first(Channel.EMAIL)
        .template("order-update")
    .ifNoOpen(Duration.ofHours(24))
    .then(Channel.PUSH)
        .content("You have an unread order update")
    .ifNoOpen(Duration.ofHours(48))
    .then(Channel.SMS)
        .content("Order update waiting — check your email")
    .execute();

Each step waits for the specified duration before escalating to the next channel.

A/B Testing

Built-in deterministic A/B testing for notifications. Variant assignment is hash-based (SHA-256) — the same recipient always gets the same variant:

notify.to(user)
    .via(Channel.EMAIL)
    .subject("Welcome!")
    .abTest("welcome-experiment")
        .variant("control", b -> b.template("welcome-v1"))
        .variant("new-design", b -> b.template("welcome-v2"))
        .split(50, 50);

Supports any number of variants with weighted splits. Deterministic hashing ensures consistent experiences across sends.

Cron Scheduling

Schedule recurring notifications with cron expressions:

ScheduledNotification job = notify.to(user)
    .via(Channel.EMAIL)
    .template("weekly-digest")
    .cron("0 9 * * MON"); // Every Monday at 9 AM

Supports standard 5-field cron syntax: minute, hour, day-of-month, month, day-of-week. Includes ranges, lists, steps, and named days/months.

Quiet Hours

Respect user preferences for notification timing:

public class User implements Notifiable {
    @Override
    public QuietHours getQuietHours() {
        return QuietHours.between(
            LocalTime.of(22, 0),  // 10 PM
            LocalTime.of(8, 0),   // 8 AM
            ZoneId.of("America/Sao_Paulo")
        );
    }

    @Override
    public Set<Channel> getOptedOutChannels() {
        return Set.of(Channel.SMS); // User opted out of SMS
    }
}

Notifications sent during quiet hours are delayed to the next allowed window. Opted-out channels are silently skipped.

Testing Utilities

TestNotifyHub provides a test-friendly wrapper with capturing channels for all built-in channel types:

@Test
void shouldSendWelcomeEmail() {
    TestNotifyHub test = TestNotifyHub.create();

    test.to("user@test.com")
        .via(Channel.EMAIL)
        .subject("Welcome")
        .content("Hello!")
        .send();

    assertThat(test.sent()).hasSize(1);
    assertThat(test.sent("email").get(0).subject()).isEqualTo("Welcome");
}

No mocking needed — TestNotifyHub captures all notifications in memory for assertions. Call test.reset() between tests.

Supported Channels

	Channel	Provider	Module
	Email	SMTP (Gmail, SES, Outlook, any)	`notify-email`
📱	SMS	Twilio	`notify-sms`
	WhatsApp	Twilio	`notify-sms`
	Slack	Incoming Webhooks	`notify-slack`
	Telegram	Bot API	`notify-telegram`
	Discord	Webhooks	`notify-discord`
👥	Microsoft Teams	Incoming Webhooks	`notify-teams`
	Push (FCM)	Firebase Cloud Messaging	`notify-push-firebase`
🔗	Webhook	Any HTTP endpoint	`notify-webhook`
	WebSocket	JDK WebSocket (`java.net.http`)	`notify-websocket`
	Google Chat	Webhooks	`notify-google-chat`
	Twitter/X	API v2 (OAuth 1.0a)	`notify-twitter`
💼	LinkedIn	REST API (OAuth 2.0)	`notify-linkedin`
	Notion	API (Integration Token)	`notify-notion`
	Twitch	Helix API (OAuth 2.0 auto-refresh)	`notify-twitch`
	YouTube	Data API v3 (OAuth auto-refresh)	`notify-youtube`
	Instagram	Meta Graph API	`notify-instagram`
📧	SendGrid	SendGrid API (delivery tracking)	`notify-sendgrid`
	TikTok Shop	TikTok Shop API (HMAC-SHA256)	`notify-tiktok-shop`
	Facebook	Graph API (Page + Messenger)	`notify-facebook`
	WhatsApp Cloud	Meta Cloud API (direct, no Twilio)	`notify-whatsapp`
☁️	AWS SNS	AWS SDK v2	`notify-aws-sns`
	Mailgun	Mailgun REST API	`notify-mailgun`
	PagerDuty	Events API v2	`notify-pagerduty`
➕	Custom	Any — implement one interface	`notify-core`

Admin Dashboard

NotifyHub includes a built-in admin dashboard for monitoring your notification system.

notify:
  admin:
    enabled: true

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-admin</artifactId>
    <version>1.0.0</version>
</dependency>

Access at /notify-admin to see:

Dashboard — metric cards (sent/failed/pending/DLQ/channels/contacts), recent activity feed, system status grid, registered channels
Analytics — Chart.js charts with send volume, channel distribution, success rate, hourly heatmap
Tracking — delivery receipts with channel filter and status badges
Dead Letter Queue — failed notifications with error details and remove action
Channels — status of each registered channel with health indicators
Audit Log — complete history of all notification events with event type filter
Audiences — manage contacts and audience segments with tag-based filtering
Status Webhook — real-time HTTP callback configuration and delivery history

Dark/light theme toggle included — persists across pages via localStorage.

Spring Boot Integration

Micrometer Metrics

Auto-configured when Micrometer is on the classpath:

<dependency>
    <groupId>io.micrometer</groupId>
    <artifactId>micrometer-core</artifactId>
</dependency>

Exposes counters and gauges via the unified EventBus:

notifyhub.notifications.sent (tags: channel)
notifyhub.notifications.failed (tags: channel)
notifyhub.notifications.retried (tags: channel)
notifyhub.notifications.rate_limited (tags: channel)
notifyhub.notifications.deduped (tags: channel)
notifyhub.notifications.circuit_opened (tags: channel)
notifyhub.notifications.circuit_closed (tags: channel)
notifyhub.notifications.send_duration (timer, tags: channel)

Actuator Health Check

Auto-configured when Spring Boot Actuator is on the classpath:

GET /actuator/health/notifyhub

{
  "status": "UP",
  "details": {
    "email": { "status": "UP", "circuitBreaker": "CLOSED" },
    "slack": { "status": "UP", "circuitBreaker": "CLOSED" },
    "totalChannels": 2,
    "availableChannels": 2
  }
}

Status: UP (all channels available), DEGRADED (some down), DOWN (all down). When circuit breaker is configured, each channel also reports its circuit state.

Actuator Info

GET /actuator/info

{
  "notifyhub": {
    "version": "1.0.0",
    "channels": ["email", "slack", "teams"],
    "tracking.enabled": true,
    "dlq.enabled": true
  }
}

OpenTelemetry Tracing

Auto-configured when Micrometer Observation and an OTel bridge are on the classpath. Add these dependencies to export distributed traces via OTLP:

<dependency>
    <groupId>io.micrometer</groupId>
    <artifactId>micrometer-tracing-bridge-otel</artifactId>
</dependency>
<dependency>
    <groupId>io.opentelemetry</groupId>
    <artifactId>opentelemetry-exporter-otlp</artifactId>
</dependency>

Configure the OTLP endpoint in application.yml:

management:
  tracing:
    sampling:
      probability: 1.0       # 100% sampling (adjust for production)
  otlp:
    tracing:
      endpoint: http://localhost:4318/v1/traces

Creates observations (spans):

notifyhub.send (tags: channel, template, outcome)
notifyhub.schedule (tags: channel, outcome)

Compatible with Jaeger, Zipkin, Grafana Tempo, Datadog, and any OTLP-compatible collector.

Webhook HMAC Signing

The Status Webhook listener supports HMAC-SHA256 request signing for security. When configured, every webhook POST includes a X-NotifyHub-Signature header that your server can use to verify the request came from NotifyHub.

notify:
  status-webhook:
    url: https://your-server.com/webhook
    signing-secret: ${WEBHOOK_SECRET}   # any secret string

Each request includes the header:

X-NotifyHub-Signature: sha256=<hex-encoded HMAC-SHA256 of request body>

Verify in your server:

Mac mac = Mac.getInstance("HmacSHA256");
mac.init(new SecretKeySpec(secret.getBytes(), "HmacSHA256"));
String expected = "sha256=" + HexFormat.of().formatHex(mac.doFinal(body.getBytes()));
boolean valid = MessageDigest.isEqual(expected.getBytes(), signature.getBytes());

Configuration Reference

Full application.yml with all options:

notify:
  channels:
    email:
      host: smtp.gmail.com
      port: 587
      username: ${GMAIL_USER}
      password: ${GMAIL_PASS}
      from: noreply@myapp.com
      from-name: MyApp
      tls: true
      ssl: false

    sms:
      account-sid: ${TWILIO_SID}
      auth-token: ${TWILIO_TOKEN}
      from-number: "+1234567890"

    whatsapp:
      account-sid: ${TWILIO_SID}
      auth-token: ${TWILIO_TOKEN}
      from-number: "+14155238886"

    slack:
      webhook-url: ${SLACK_WEBHOOK}
      recipients:                          # named aliases (optional)
        engineering: https://hooks.slack.com/services/XXX
        marketing: https://hooks.slack.com/services/YYY

    telegram:
      bot-token: ${TELEGRAM_BOT_TOKEN}
      chat-id: ${TELEGRAM_CHAT_ID}
      recipients:                          # named aliases (optional)
        alerts: "-1001234567890"
        devops: "-1009876543210"

    discord:
      webhook-url: ${DISCORD_WEBHOOK}
      username: NotifyHub
      avatar-url: https://example.com/logo.png
      recipients:                          # named aliases (optional)
        alerts: https://discord.com/api/webhooks/111/aaa
        devops: https://discord.com/api/webhooks/222/bbb

    teams:
      webhook-url: ${TEAMS_WEBHOOK}
      recipients:                          # named aliases (optional)
        general: https://outlook.office.com/webhook/XXX

    push:
      credentials-path: ${FIREBASE_CREDENTIALS}
      project-id: ${FIREBASE_PROJECT_ID}

    webhooks:
      - name: pagerduty
        url: https://events.pagerduty.com/v2/enqueue
        headers:
          Authorization: "Token ${PAGERDUTY_TOKEN}"
        payload-template: '{"summary":"{{content}}"}'

    websocket:
      uri: wss://echo.example.com/ws
      timeout-ms: 10000
      reconnect-enabled: true
      reconnect-delay-ms: 5000
      max-reconnect-attempts: 3
      headers:
        Authorization: "Bearer ${WS_TOKEN}"
      message-format: '{"type":"notification","content":"{{content}}"}'

    google-chat:
      webhook-url: ${GOOGLE_CHAT_WEBHOOK}
      timeout-ms: 10000
      recipients:                          # named aliases (optional)
        team-a: https://chat.googleapis.com/v1/spaces/XXX/messages?key=YYY
        team-b: https://chat.googleapis.com/v1/spaces/ZZZ/messages?key=WWW

  retry:
    max-attempts: 3
    strategy: exponential

  rate-limit:
    enabled: true
    max-requests: 100
    window: 1m
    channels:
      email:
        max-requests: 50
        window: 1m

  tracking:
    enabled: true
    type: memory         # memory | jpa
    dlq-enabled: true

  deduplication:
    enabled: true
    ttl: 24h
    strategy: content-hash  # content-hash | explicit-key | both

  admin:
    enabled: true

Without Spring Boot

NotifyHub works without Spring — use the builder directly:

NotifyHub notify = NotifyHub.builder()
    .templateEngine(new MustacheTemplateEngine())
    .channel(new SmtpEmailChannel(
        SmtpConfig.builder()
            .host("smtp.gmail.com").port(587)
            .username("user@gmail.com").password("app-password")
            .from("noreply@myapp.com").tls(true)
            .build()
    ))
    .channel(new SlackChannel(
        SlackConfig.builder()
            .webhookUrl("https://hooks.slack.com/services/XXX/YYY/ZZZ")
            .recipients(Map.of("engineering", "https://hooks.slack.com/services/AAA/BBB/CCC"))
            .build()
    ))
    .channel(new TeamsChannel(
        TeamsConfig.builder()
            .webhookUrl("https://outlook.office.com/webhook/XXX/YYY/ZZZ")
            .build()
    ))
    .channel(new WebhookChannel(
        WebhookConfig.builder()
            .name("pagerduty")
            .url("https://events.pagerduty.com/v2/enqueue")
            .payloadTemplate("{\"summary\":\"{{content}}\"}")
            .build()
    ))
    .channel(new WebSocketChannel(
        WebSocketConfig.builder()
            .uri("wss://echo.example.com/ws")
            .messageFormat("{\"text\":\"{{content}}\"}")
            .build()
    ))
    .channel(new GoogleChatChannel(
        GoogleChatConfig.builder()
            .webhookUrl("https://chat.googleapis.com/v1/spaces/XXX/messages?key=YYY")
            .build()
    ))
    .deduplicationStore(new InMemoryDeduplicationStore(Duration.ofHours(24)))
    .defaultRetryPolicy(RetryPolicy.exponential(3))
    .rateLimiter(new TokenBucketRateLimiter(
        RateLimitConfig.perMinute(100)))
    .deadLetterQueue(new InMemoryDeadLetterQueue())
    .tracker(new InMemoryNotificationTracker())
    .circuitBreaker(CircuitBreakerConfig.defaults())
    .bulkhead(BulkheadConfig.defaults())
    .build();

// Sync
notify.to("user@email.com")
    .via(Channel.EMAIL)
    .subject("Hello!")
    .content("Welcome to the app!")
    .send();

// Async
notify.to("#general")
    .via(Channel.SLACK)
    .content("Deploy complete!")
    .sendAsync();

// Tracked
DeliveryReceipt receipt = notify.to(user)
    .via(Channel.EMAIL)
    .content("Invoice attached")
    .sendTracked();

// Scheduled
notify.to(user)
    .via(Channel.EMAIL)
    .content("Reminder!")
    .schedule(Duration.ofMinutes(30));

// Batch
notify.toAll(List.of("a@test.com", "b@test.com"))
    .via(Channel.EMAIL)
    .template("announcement")
    .send();

Only notify-core + channel modules needed. No Spring dependency.

MCP Server (AI Agents)

NotifyHub includes an MCP (Model Context Protocol) server that exposes all notification channels as tools for AI agents like Claude Desktop, Claude Code, Cursor, and any MCP-compatible client.

How it works

The notify-mcp module is a standalone Java application that communicates via STDIO using the JSON-RPC protocol. AI agents discover the available tools and can send notifications through any configured channel.

Setup

1. Build the MCP server:

mvn clean package -pl notify-mcp -am -DskipTests

2. Configure in Claude Desktop (claude_desktop_config.json):

{
  "mcpServers": {
    "notify-hub": {
      "command": "java",
      "args": ["-jar", "path/to/notify-mcp-1.0.0.jar"],
      "env": {
        "NOTIFY_CHANNELS_EMAIL_HOST": "smtp.gmail.com",
        "NOTIFY_CHANNELS_EMAIL_PORT": "587",
        "NOTIFY_CHANNELS_EMAIL_USERNAME": "you@gmail.com",
        "NOTIFY_CHANNELS_EMAIL_PASSWORD": "app-password",
        "NOTIFY_CHANNELS_SLACK_WEBHOOK_URL": "https://hooks.slack.com/...",
        "NOTIFY_CHANNELS_DISCORD_WEBHOOK_URL": "https://discord.com/api/webhooks/..."
      }
    }
  }
}

Or for Claude Code (.mcp.json in project root):

{
  "mcpServers": {
    "notify-hub": {
      "command": "java",
      "args": ["-jar", "path/to/notify-mcp-1.0.0.jar"],
      "env": {
        "NOTIFY_CHANNELS_DISCORD_WEBHOOK_URL": "https://discord.com/api/webhooks/..."
      }
    }
  }
}

Available MCP Tools

Tool	Description	Required Params
`send_notification`	Send via any channel (generic)	`channel`, `recipient`, `body` or `template`
`send_email`	Send email	`to`, `body` or `template`
`send_sms`	Send SMS via Twilio	`phone`, `body` or `template`
`send_slack`	Send to Slack channel	`recipient`, `body` or `template`
`send_telegram`	Send via Telegram Bot	`recipient`, `body` or `template`
`send_discord`	Send to Discord channel	`recipient`, `body` or `template`
`send_whatsapp`	Send WhatsApp via Twilio	`phone`, `body` or `template`
`send_teams`	Send to Microsoft Teams	`recipient`, `body` or `template`
`send_google_chat`	Send to Google Chat	`recipient`, `body` or `template`
`send_push`	Send push via Firebase	`push_token`, `body`
`send_twitter`	Post a tweet on Twitter/X	`body` or `template`
`send_linkedin`	Publish a post on LinkedIn	`body` or `template`
`send_notion`	Create a page in Notion	`recipient`, `body` or `template`
`send_twitch`	Send Twitch chat message + polls	`recipient`, `body` or `template`
`send_youtube`	Send YouTube live chat message	`recipient`, `body` or `template`
`send_instagram`	Send Instagram DM or feed post	`recipient`, `body` or `template`
`send_multi_channel`	Send to multiple channels	`channels[]`, `recipient`, `body` or `template`
`send_batch`	Send to multiple recipients at once	`recipients[]`, `channel`, `body` or `template`
`send_to_audience`	Send to a named audience	`audience`, `channel`, `body` or `template`
`list_channels`	List configured channels	(none)
`list_delivery_receipts`	Query delivery history	(none)
`list_dead_letters`	View failed notifications (DLQ)	(none)
`create_contact`	Create a contact with tags	`name`
`list_contacts`	List contacts (filter by tag)	(none)
`create_audience`	Create audience with tag filters	`name`, `tags[]`
`list_audiences`	List audiences with contact counts	(none)
`get_analytics`	Delivery stats by channel/status	(none)
`send_tiktok_shop`	Send TikTok Shop notification	`recipient`, `body` or `template`
`send_facebook`	Send Facebook page post or Messenger DM	`recipient`, `body` or `template`
`check_email_status`	Check SendGrid email delivery status	`message_id`
`schedule_notification`	Schedule a notification for later delivery	`channel`, `recipient`, `body`, `send_at`
`list_scheduled_notifications`	List all scheduled notifications	(none)
`cancel_scheduled_notification`	Cancel a pending scheduled notification	`notification_id`

All send tools optionally accept: subject, template, params, priority.

Usage example (from an AI agent)

Once configured, you can simply ask your AI agent:

"Send a Discord message to #alerts saying the deploy is complete"

The agent will call the send_discord tool with the appropriate parameters.

Docker

Run the MCP server without Java installed — only Docker required:

# Build
docker build -t notifyhub-mcp .

# Run with Discord
docker run -i --rm \
  -e NOTIFY_CHANNELS_DISCORD_WEBHOOK_URL="https://discord.com/api/webhooks/..." \
  -e NOTIFY_CHANNELS_DISCORD_USERNAME="NotifyHub" \
  gabrielbbal10/notifyhub-mcp

# Run with multiple Discord channels + Email
docker run -i --rm \
  -e NOTIFY_CHANNELS_DISCORD_WEBHOOK_URL="https://discord.com/api/webhooks/..." \
  -e NOTIFY_CHANNELS_DISCORD_USERNAME="NotifyHub" \
  -e NOTIFY_CHANNELS_DISCORD_RECIPIENTS_ALERTS="https://discord.com/api/webhooks/111/aaa" \
  -e NOTIFY_CHANNELS_DISCORD_RECIPIENTS_DEVOPS="https://discord.com/api/webhooks/222/bbb" \
  -e NOTIFY_CHANNELS_EMAIL_HOST="smtp.gmail.com" \
  -e NOTIFY_CHANNELS_EMAIL_PORT="587" \
  -e NOTIFY_CHANNELS_EMAIL_USERNAME="you@gmail.com" \
  -e NOTIFY_CHANNELS_EMAIL_PASSWORD="app-password" \
  -e NOTIFY_CHANNELS_EMAIL_FROM="you@gmail.com" \
  gabrielbbal10/notifyhub-mcp

Configure in Claude Code (.mcp.json):

{
  "mcpServers": {
    "notify-hub": {
      "command": "docker",
      "args": ["run", "-i", "--rm",
        "-e", "NOTIFY_CHANNELS_DISCORD_WEBHOOK_URL=https://discord.com/api/webhooks/...",
        "-e", "NOTIFY_CHANNELS_DISCORD_USERNAME=NotifyHub",
        "-e", "NOTIFY_CHANNELS_DISCORD_RECIPIENTS_ALERTS=https://discord.com/api/webhooks/111/aaa",
        "gabrielbbal10/notifyhub-mcp"
      ]
    }
  }
}

Docker REST API

Run a full REST API with Swagger UI — no Java required, just Docker:

docker run -d -p 8080:8080 \
  -e NOTIFY_CHANNELS_EMAIL_USERNAME=you@gmail.com \
  -e NOTIFY_CHANNELS_EMAIL_PASSWORD=your-app-password \
  -e NOTIFY_CHANNELS_EMAIL_FROM=you@gmail.com \
  gabrielbbal10/notifyhub-api:latest

Open http://localhost:8080/swagger-ui.html for interactive API docs.

Environment variables — same for both MCP and API images, add only the channels you need:

Channel	Variable	Required	Example
Email	`NOTIFY_CHANNELS_EMAIL_HOST`	No (default: `smtp.gmail.com`)	`smtp.gmail.com`
	`NOTIFY_CHANNELS_EMAIL_PORT`	No (default: `587`)	`587`
	`NOTIFY_CHANNELS_EMAIL_USERNAME`	Yes (for email)	`you@gmail.com`
	`NOTIFY_CHANNELS_EMAIL_PASSWORD`	Yes (for email)	`abcd efgh ijkl mnop` (App Password)
	`NOTIFY_CHANNELS_EMAIL_FROM`	Yes (for email)	`you@gmail.com`
Discord	`NOTIFY_CHANNELS_DISCORD_WEBHOOK_URL`	Yes (for discord)	`https://discord.com/api/webhooks/...`
	`NOTIFY_CHANNELS_DISCORD_USERNAME`	No	`NotifyHub`
	`NOTIFY_CHANNELS_DISCORD_AVATAR_URL`	No	`https://example.com/avatar.png`
	`NOTIFY_CHANNELS_DISCORD_RECIPIENTS_<NAME>`	No	Named alias webhook URL
Slack	`NOTIFY_CHANNELS_SLACK_WEBHOOK_URL`	Yes (for slack)	`https://hooks.slack.com/services/...`
	`NOTIFY_CHANNELS_SLACK_RECIPIENTS_<NAME>`	No	Named alias webhook URL
Telegram	`NOTIFY_CHANNELS_TELEGRAM_BOT_TOKEN`	Yes (for telegram)	`123456:ABC-DEF...`
	`NOTIFY_CHANNELS_TELEGRAM_CHAT_ID`	Yes (for telegram)	`123456789`
	`NOTIFY_CHANNELS_TELEGRAM_RECIPIENTS_<NAME>`	No	Named alias chat ID
Google Chat	`NOTIFY_CHANNELS_GOOGLE_CHAT_WEBHOOK_URL`	Yes (for gchat)	`https://chat.googleapis.com/v1/spaces/...`
	`NOTIFY_CHANNELS_GOOGLE_CHAT_RECIPIENTS_<NAME>`	No	Named alias webhook URL
Teams	`NOTIFY_CHANNELS_TEAMS_WEBHOOK_URL`	Yes (for teams)	`https://outlook.office.com/webhook/...`
	`NOTIFY_CHANNELS_TEAMS_RECIPIENTS_<NAME>`	No	Named alias webhook URL
SMS	`NOTIFY_CHANNELS_SMS_ACCOUNT_SID`	Yes (for sms)	Twilio Account SID
	`NOTIFY_CHANNELS_SMS_AUTH_TOKEN`	Yes (for sms)	Twilio Auth Token
	`NOTIFY_CHANNELS_SMS_FROM_NUMBER`	Yes (for sms)	`+12025551234`
WhatsApp	`NOTIFY_CHANNELS_WHATSAPP_ACCOUNT_SID`	Yes (for whatsapp)	Twilio Account SID
	`NOTIFY_CHANNELS_WHATSAPP_AUTH_TOKEN`	Yes (for whatsapp)	Twilio Auth Token
	`NOTIFY_CHANNELS_WHATSAPP_FROM_NUMBER`	Yes (for whatsapp)	`+14155238886`

Example with multiple channels:

docker run -d -p 8080:8080 \
  -e NOTIFY_CHANNELS_EMAIL_USERNAME=you@gmail.com \
  -e NOTIFY_CHANNELS_EMAIL_PASSWORD=your-app-password \
  -e NOTIFY_CHANNELS_EMAIL_FROM=you@gmail.com \
  -e NOTIFY_CHANNELS_DISCORD_WEBHOOK_URL="https://discord.com/api/webhooks/..." \
  -e NOTIFY_CHANNELS_DISCORD_USERNAME="NotifyHub" \
  -e NOTIFY_CHANNELS_TELEGRAM_BOT_TOKEN="123456:ABC-DEF..." \
  -e NOTIFY_CHANNELS_TELEGRAM_CHAT_ID="123456789" \
  -e NOTIFY_CHANNELS_GOOGLE_CHAT_WEBHOOK_URL="https://chat.googleapis.com/v1/spaces/..." \
  gabrielbbal10/notifyhub-api:latest

Usage from any language:

# Send email
curl -X POST "http://localhost:8080/send/email?to=user@example.com&subject=Hello&body=Hi!"

# Send Discord
curl -X POST "http://localhost:8080/send/discord?message=Deploy done!"

# Send Telegram
curl -X POST "http://localhost:8080/send/telegram?chatId=123456789&message=Alert!"

# Send Google Chat
curl -X POST "http://localhost:8080/send/google-chat?message=Build passed!"

Docker Hub: gabrielbbal10/notifyhub-api

Running the Demo

The demo app showcases every feature with a built-in SMTP server — zero external config needed.

git clone https://github.com/GabrielBBaldez/notify-hub.git
cd notify-hub
mvn clean install -DskipTests

# Run the demo
mvn -pl notify-demo spring-boot:run

Then open:

http://localhost:8080 — API endpoints
http://localhost:8080/notify-admin — Admin dashboard

Demo Endpoints

Method	Endpoint	Description
`GET`	`/`	Home — lists all endpoints
`POST`	`/send/email`	Send a simple email
`POST`	`/send/template`	Send email with Mustache template
`POST`	`/send/notifiable`	Send to a Notifiable entity
`POST`	`/send/sms`	Send SMS (requires Twilio)
`POST`	`/send/whatsapp`	Send WhatsApp (requires Twilio)
`POST`	`/send/telegram`	Send to Telegram via Bot
`POST`	`/send/discord`	Send to Discord via Webhook
`POST`	`/send/slack`	Send to Slack channel
`POST`	`/send/teams`	Send to Microsoft Teams via Webhook
`POST`	`/send/google-chat`	Send to Google Chat via Webhook
`POST`	`/send/push`	Send push notification via Firebase
`POST`	`/send/websocket`	Send message via WebSocket
`POST`	`/send/multi`	Send to email + Slack simultaneously
`POST`	`/send/fallback`	Test fallback (email fails -> Slack)
`POST`	`/send/tracked`	Send with delivery tracking
`POST`	`/send/scheduled`	Schedule notification for future
`GET`	`/tracking`	Delivery tracking history
`GET`	`/notify-admin`	Admin dashboard
`GET`	`/inbox`	View captured emails
`DELETE`	`/inbox`	Clear all inboxes

Architecture

notify-hub/
├── notify-core/                          # Zero Spring dependency
│   ├── NotifyHub                         # Thin facade — delegates to executor/scheduler/eventbus
│   ├── NotificationExecutor              # Channel resolution, send logic, fallback chains
│   ├── NotificationScheduler             # Scheduling with delay/cancel/list
│   ├── NotificationBuilder               # Fluent builder (send/async/tracked/scheduled)
│   ├── BatchNotificationBuilder          # Batch send to multiple recipients
│   ├── Notification                      # Immutable notification object
│   ├── Channel / ChannelRef              # Built-in + custom channel refs
│   ├── Priority                          # URGENT, HIGH, NORMAL, LOW
│   ├── Notifiable                        # Recipient interface (i18n + routing + quiet hours)
│   ├── NotificationChannel               # Channel SPI (implement this!)
│   ├── QuietHours                        # Per-recipient quiet time windows
│   ├── pipeline/                         # Resilience handler chain
│   │   ├── SendPipeline                  # Assembles: Dedup → RateLimit → CircuitBreaker → Template → Retry
│   │   ├── SendHandler                   # Handler chain interface
│   │   ├── SendContext                   # Per-send state (channel, builder, notification)
│   │   ├── DeduplicationHandler          # Skip duplicates
│   │   ├── RateLimitHandler              # Enforce per-channel limits
│   │   ├── CircuitBreakerHandler         # Short-circuit failing channels
│   │   ├── TemplateHandler               # Build + render notification
│   │   └── RetrySendHandler              # Terminal: retry with backoff → DLQ
│   ├── resilience/                       # Resilience primitives
│   │   ├── ChannelCircuitBreaker         # Per-channel circuit breaker (sliding window)
│   │   ├── CircuitBreakerConfig          # Thresholds + durations
│   │   ├── CircuitState                  # CLOSED, OPEN, HALF_OPEN
│   │   └── BulkheadConfig               # Per-channel concurrency limits
│   ├── event/                            # Unified event system
│   │   ├── NotificationEventBus          # Publish events to listeners
│   │   ├── NotificationEvent             # Immutable event record
│   │   ├── EventType                     # SENT, FAILED, RETRIED, RATE_LIMITED, DEDUPED, CIRCUIT_*
│   │   ├── NotificationEventListener     # Listener interface
│   │   └── LegacyListenerAdapter         # Bridge: old NotificationListener → EventBus
│   ├── orchestration/                    # Multi-step notification workflows
│   │   ├── OrchestrationBuilder          # first(EMAIL).ifNoOpen(24h).then(PUSH)
│   │   └── OrchestrationStep            # Individual step record
│   ├── abtest/                           # A/B testing
│   │   └── AbTestBuilder                # Deterministic SHA-256 variant selection
│   ├── schedule/                         # Cron support
│   │   └── CronExpression               # Lightweight 5-field cron parser
│   ├── attachment/                       # File attachments
│   │   └── Attachment                    # Email file attachments
│   ├── testing/                          # Test utilities
│   │   ├── TestNotifyHub                 # Test wrapper with capturing channels
│   │   └── SentNotification             # Captured notification record
│   ├── RateLimiter / TokenBucket         # Rate limiting
│   ├── NotificationRouter / RoutingRule  # Conditional routing
│   ├── MustacheTemplateEngine            # Template engine (i18n-aware + versioning)
│   ├── DeduplicationStore                # Dedup interface (in-memory impl)
│   └── RetryPolicy                       # Retry + backoff strategies
│
├── notify-channels/
│   ├── notify-email/                     # SMTP email (Jakarta Mail + attachments)
│   ├── notify-sms/                       # Twilio SMS + WhatsApp
│   ├── notify-slack/                     # Slack webhooks (JDK HttpClient)
│   ├── notify-telegram/                  # Telegram Bot API (JDK HttpClient)
│   ├── notify-discord/                   # Discord webhooks (JDK HttpClient)
│   ├── notify-teams/                     # Microsoft Teams webhooks (JDK HttpClient)
│   ├── notify-push-firebase/             # Firebase Cloud Messaging (FCM)
│   ├── notify-webhook/                   # Generic webhook (configurable)
│   ├── notify-websocket/                 # WebSocket (JDK java.net.http)
│   ├── notify-google-chat/              # Google Chat webhooks (JDK HttpClient)
│   ├── notify-twitch/                   # Twitch chat + polls via Helix API (JDK HttpClient)
│   ├── notify-youtube/                  # YouTube live chat via Data API v3 (JDK HttpClient)
│   ├── notify-instagram/               # Instagram DM + feed via Meta Graph API (JDK HttpClient)
│   ├── notify-sendgrid/                # SendGrid email with delivery tracking (JDK HttpClient)
│   ├── notify-tiktok-shop/             # TikTok Shop API (HMAC-SHA256, JDK HttpClient)
│   ├── notify-facebook/                # Facebook Graph API (Page + Messenger)
│   ├── notify-whatsapp/                # WhatsApp Cloud API (Meta Graph API, no Twilio)
│   ├── notify-aws-sns/                 # AWS SNS (AWS SDK v2)
│   ├── notify-mailgun/                 # Mailgun transactional email (JDK HttpClient)
│   ├── notify-pagerduty/              # PagerDuty Events API v2 (JDK HttpClient)
│   └── notify-channel-template/       # Template/archetype for creating new channels
│
├── notify-tracker-jpa/                   # JPA-backed delivery tracker
├── notify-audit-jpa/                     # JPA-backed audit logging
│
├── notify-spring-boot-starter/           # Auto-config for Spring Boot
│   ├── NotifyAutoConfiguration           # Auto-discovers all channels + event listeners
│   ├── MetricsEventListener              # Micrometer metrics via EventBus
│   ├── TracingNotificationListener       # OpenTelemetry tracing (Observation API)
│   ├── NotifyHubHealthIndicator          # Actuator health (+ circuit breaker status)
│   ├── NotifyHubInfoContributor          # Actuator info endpoint
│   ├── SpringEventNotificationListener   # Spring ApplicationEvents
│   └── NotifyProperties                  # application.yml binding
│
├── notify-admin/                         # Admin dashboard (Thymeleaf)
│   └── NotifyAdminController             # /notify-admin/*
│
├── notify-mcp/                           # MCP Server for AI agents
│   ├── NotifyMcpServer                   # Spring Boot headless main
│   ├── McpServerRunner                   # STDIO MCP server bootstrap
│   └── tools/                            # 36 MCP tools (send, batch, audiences, DLQ, analytics)
│
├── notify-queue-rabbitmq/                # RabbitMQ integration
├── notify-queue-kafka/                   # Kafka integration
│
└── notify-demo/                          # Demo app (run it!)

Resilience Pipeline

Every notification passes through a handler chain before hitting the channel:

Deduplication → Rate Limit → Circuit Breaker → Template Rendering → Retry + Send → DLQ

Each handler can short-circuit (e.g., dedup skips duplicates, circuit breaker rejects when open). The pipeline is fully optional — handlers are skipped when their dependency is null.

Design Principles

notify-core has zero Spring dependency — use it in any Java project
Channels are pluggable — implement NotificationChannel, register as a Spring bean
Slack, Telegram, Discord, Teams, WebSocket, Google Chat use zero external SDKs — only JDK java.net.http.HttpClient
Template engine is replaceable — implement TemplateEngine interface
Spring Boot starter auto-configures everything — just add the dependency
Async support — sendAsync() and sendAllAsync() with CompletableFuture
Conditional auto-config — channel beans only load when their module is on classpath
Unified event system — NotificationEventBus replaces scattered listener calls, backward-compatible via LegacyListenerAdapter

Maven Central

NotifyHub is published on Maven Central. No extra repositories needed.

Search on Maven Central: io.github.gabrielbbaldez

Available Modules

Below is every module, what it does, when you need it, and how to add it.

`notify-spring-boot-starter` — The Main Dependency

What it does: Auto-configures NotifyHub inside a Spring Boot application. Automatically discovers channel beans, wires retry policies, tracking, rate limiting, DLQ, Micrometer metrics, OpenTelemetry tracing, Actuator health checks, and Spring events. Includes notify-core and notify-email transitively.

When to use: You're building a Spring Boot app and want automatic setup. This is the only required dependency for most projects.

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-spring-boot-starter</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-core` — Core API (No Spring)

What it does: Contains the entire fluent API (NotifyHub, NotificationBuilder, Channel, Notification, Priority, Attachment, RetryPolicy), plus interfaces for channels, templates, tracking, DLQ, rate limiting, and routing. Has zero Spring dependency — uses only SLF4J and Mustache.

When to use: You want to use NotifyHub in a plain Java project without Spring Boot, or you're building a library/framework on top of it.

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-core</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-email` — SMTP Email Channel

What it does: Sends emails via any SMTP server (Gmail, Outlook, Amazon SES, Mailtrap, etc). Supports HTML and plain text, file attachments, TLS/SSL, and custom sender name. Uses Jakarta Mail internally.

When to use: You want to send email notifications. Already included by notify-spring-boot-starter.

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-email</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-sms` — Twilio SMS + WhatsApp Channel

What it does: Sends SMS and WhatsApp messages through the Twilio API. Handles phone number formatting (E.164) and the whatsapp: prefix automatically.

When to use: You need to send SMS or WhatsApp messages. Requires a Twilio account with Account SID, Auth Token, and a phone number.

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-sms</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-slack` — Slack Webhook Channel

What it does: Sends messages to a Slack channel via Incoming Webhooks. Uses the JDK HttpClient — no external SDK needed.

When to use: You want to post notifications to Slack. Requires a Slack Incoming Webhook URL (created at api.slack.com/apps).

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-slack</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-telegram` — Telegram Bot Channel

What it does: Sends messages to Telegram chats/groups/channels via the Bot API. Supports a default chat ID and per-notification targeting. Uses the JDK HttpClient.

When to use: You want to send Telegram messages. Requires a bot token from @BotFather.

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-telegram</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-discord` — Discord Webhook Channel

What it does: Sends messages to a Discord channel via Webhooks. Supports custom bot username and avatar. Uses the JDK HttpClient.

When to use: You want to post notifications to Discord. Requires a Discord webhook URL (channel Settings > Integrations > Webhooks).

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-discord</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-teams` — Microsoft Teams Channel

What it does: Sends MessageCard notifications to a Teams channel via Incoming Webhooks. Uses the JDK HttpClient.

When to use: You want to post notifications to Microsoft Teams. Requires a Teams Incoming Webhook URL (channel > Connectors > Incoming Webhook).

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-teams</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-push-firebase` — Firebase Cloud Messaging (FCM)

What it does: Sends push notifications to mobile devices (Android/iOS) and web apps via Firebase Cloud Messaging. Uses the Firebase Admin SDK with service account credentials.

When to use: You want to send push notifications to mobile apps. Requires a Firebase project with a service account JSON credentials file.

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-push-firebase</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-webhook` — Generic Webhook Channel

What it does: Sends notifications to any HTTP endpoint (REST APIs, PagerDuty, Datadog, custom services). Supports configurable payload templates with {{recipient}}, {{subject}}, {{content}} placeholders, custom headers, PUT/POST methods, and timeouts.

When to use: You want to integrate with any external service that has an HTTP API, or create custom webhook integrations.

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-webhook</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-websocket` — WebSocket Channel

What it does: Sends notifications over WebSocket connections using the JDK java.net.http.WebSocket API. Supports configurable message format with {{recipient}}, {{subject}}, {{content}} placeholders, custom headers, auto-reconnect with backoff, and connection timeout. Zero external dependencies.

When to use: You want to send real-time notifications over WebSocket to a server (e.g., live dashboards, chat systems, or custom WebSocket consumers).

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-websocket</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-google-chat` — Google Chat Channel

What it does: Sends messages to Google Chat spaces via Incoming Webhooks. Posts JSON payloads using the JDK HttpClient — no external SDK needed.

When to use: You want to send notifications to a Google Chat space. Requires a Google Chat webhook URL (space Settings > Apps & integrations > Webhooks).

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-google-chat</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-twitch` — Twitch Channel

What it does: Sends chat messages and polls to Twitch channels via the Helix API. Uses the JDK HttpClient — no external SDK needed.

When to use: You want to send notifications to Twitch chat or create polls. Requires Twitch API OAuth 2.0 credentials (Client ID + OAuth token).

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-twitch</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-youtube` — YouTube Channel

What it does: Sends live chat messages to YouTube live streams via the YouTube Data API v3. Uses the JDK HttpClient — no external SDK needed.

When to use: You want to send notifications to YouTube live chat. Requires a Google API key or OAuth 2.0 credentials with YouTube Data API v3 enabled.

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-youtube</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-instagram` — Instagram Channel

What it does: Sends DMs and feed posts via the Meta Graph API (Instagram Graph API). Uses the JDK HttpClient — no external SDK needed.

When to use: You want to send notifications via Instagram. Requires a Facebook Developer account with Instagram Graph API access.

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-instagram</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-sendgrid` — SendGrid Email Channel

What it does: Sends transactional emails via SendGrid API with built-in delivery event tracking (delivered, opened, clicked, bounced). Uses the JDK HttpClient — no external SDK needed.

When to use: You want email delivery tracking beyond basic SMTP, or you already use SendGrid as your email provider.

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-sendgrid</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-tiktok-shop` — TikTok Shop Channel

What it does: Sends messages to TikTok Shop sellers via the TikTok Shop API. Handles HMAC-SHA256 request signing automatically. Uses the JDK HttpClient.

When to use: You want to send notifications to TikTok Shop sellers (order updates, customer messages).

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-tiktok-shop</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-facebook` — Facebook Channel

What it does: Sends Facebook Page posts and Messenger messages via the Graph API. Uses the JDK HttpClient — no external SDK needed.

When to use: You want to post to Facebook Pages or send Messenger messages.

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-facebook</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-whatsapp` — WhatsApp Cloud API Channel

What it does: Sends WhatsApp messages directly via Meta's Cloud API (no Twilio needed). Uses the JDK HttpClient — zero external dependencies.

When to use: You want to send WhatsApp messages using Meta's official Cloud API instead of Twilio.

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-whatsapp</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-aws-sns` — AWS SNS Channel

What it does: Publishes messages to AWS SNS topics or sends direct SMS via AWS Simple Notification Service. Uses AWS SDK v2.

When to use: You're already in the AWS ecosystem and want to use SNS for notifications.

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-aws-sns</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-mailgun` — Mailgun Channel

What it does: Sends transactional emails via Mailgun REST API. Uses the JDK HttpClient — no external SDK needed.

When to use: You use Mailgun as your email provider.

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-mailgun</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-pagerduty` — PagerDuty Channel

What it does: Creates PagerDuty incidents via the Events API v2. Uses the JDK HttpClient — no external SDK needed.

When to use: You want to trigger PagerDuty alerts/incidents from your notification pipeline.

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-pagerduty</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-tracker-jpa` — JPA Delivery Tracker

What it does: Persists delivery receipts to a relational database (MySQL, PostgreSQL, H2, etc.) using Spring Data JPA. Stores notification ID, channel, recipient, status, timestamp, and error messages. Provides query methods for filtering and counting.

When to use: You want delivery tracking data to survive restarts (instead of the default in-memory tracker). Requires Spring Data JPA and a database on the classpath.

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-tracker-jpa</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-admin` — Admin Dashboard

What it does: Provides a built-in web UI at /notify-admin with 4 pages: Dashboard (overview metrics), Tracking (delivery receipts), DLQ (failed notifications), and Channels (status). Built with Thymeleaf, dark theme, fully responsive.

When to use: You want a visual admin panel to monitor your notification system without building one from scratch. Requires notify.admin.enabled=true in your config.

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-admin</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-queue-rabbitmq` — RabbitMQ Message Queue

What it does: Adds async notification processing via RabbitMQ. Includes a producer (enqueue notifications), a consumer (reads from queue and sends via NotifyHub), and Spring Boot auto-configuration with exchange/queue/binding setup.

When to use: You need to decouple notification sending from your main application flow, or you're in a microservice architecture where one service enqueues and another sends.

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-queue-rabbitmq</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-queue-kafka` — Apache Kafka Message Queue

What it does: Same as RabbitMQ module but uses Apache Kafka as the message broker. Sends notifications to a Kafka topic with channel:recipient as the message key for partition ordering.

When to use: You're already using Kafka in your infrastructure, or you need high-throughput notification processing at scale.

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-queue-kafka</artifactId>
    <version>1.0.0</version>
</dependency>

`notify-mcp` — MCP Server for AI Agents

What it does: Exposes all NotifyHub channels as MCP (Model Context Protocol) tools, allowing AI agents (Claude Desktop, Claude Code, Cursor) to send notifications through natural language commands. Runs as a headless Spring Boot app communicating via STDIO JSON-RPC. Provides 27 tools: send via any channel, batch send, audience management, DLQ monitoring, and delivery analytics.

When to use: You want AI agents to send notifications on your behalf. Configure the JAR path in your MCP client's config file and the agent will discover all available tools automatically.

<dependency>
    <groupId>io.github.gabrielbbaldez</groupId>
    <artifactId>notify-mcp</artifactId>
    <version>1.0.0</version>
</dependency>

What Do I Need?

I want to...	Add these dependencies
Send emails from Spring Boot	`notify-spring-boot-starter` (already includes email)
Send SMS or WhatsApp	`notify-spring-boot-starter` + `notify-sms`
Send to Slack	`notify-spring-boot-starter` + `notify-slack`
Send to Telegram	`notify-spring-boot-starter` + `notify-telegram`
Send to Discord	`notify-spring-boot-starter` + `notify-discord`
Send to Microsoft Teams	`notify-spring-boot-starter` + `notify-teams`
Send mobile push (FCM)	`notify-spring-boot-starter` + `notify-push-firebase`
Send to any HTTP API	`notify-spring-boot-starter` + `notify-webhook`
Send via WebSocket	`notify-spring-boot-starter` + `notify-websocket`
Send to Google Chat	`notify-spring-boot-starter` + `notify-google-chat`
Send to Twitch chat	`notify-spring-boot-starter` + `notify-twitch`
Send to YouTube live chat	`notify-spring-boot-starter` + `notify-youtube`
Send to Instagram	`notify-spring-boot-starter` + `notify-instagram`
Send via SendGrid (with tracking)	`notify-spring-boot-starter` + `notify-sendgrid`
Send to TikTok Shop	`notify-spring-boot-starter` + `notify-tiktok-shop`
Send to Facebook Page/Messenger	`notify-spring-boot-starter` + `notify-facebook`
Send WhatsApp via Cloud API	`notify-spring-boot-starter` + `notify-whatsapp`
Send via AWS SNS	`notify-spring-boot-starter` + `notify-aws-sns`
Send via Mailgun	`notify-spring-boot-starter` + `notify-mailgun`
Create PagerDuty incidents	`notify-spring-boot-starter` + `notify-pagerduty`
Prevent duplicate sends	`notify-spring-boot-starter` (built-in, config-driven)
A/B test templates	`notify-spring-boot-starter` (built-in, use `.templateVersion()`)
Persist tracking to database	`notify-spring-boot-starter` + `notify-tracker-jpa`
Admin dashboard UI	`notify-spring-boot-starter` + `notify-admin`
Use without Spring Boot	`notify-core` + channel modules you need
Async processing via RabbitMQ	`notify-spring-boot-starter` + `notify-queue-rabbitmq`
Async processing via Kafka	`notify-spring-boot-starter` + `notify-queue-kafka`
Let AI agents send notifications	`notify-mcp` (standalone JAR)
Everything at once	`notify-spring-boot-starter` + all channel modules above

Roadmap

Requirements

Java 17+
Spring Boot 3.x (for starter — optional, core works standalone)
Maven 3.8+ (for building)

License

MIT License — see LICENSE for details.

Built by Gabriel Baldez

NotifyHub — Unified Notification MCP Server