Welcome! In this unit, we will delve into implementing Pub/Sub for notifications within our Redis-based backend system project. You've already learned how to manage user data, handle transactions, and use streams for event logging. Now, we'll add another powerful feature to our project: real-time notifications using Redis Pub/Sub (publish/subscribe). This will enable our system to send and receive messages instantaneously.

In this unit, we'll focus on creating a simple real-time notification system using Redis Pub/Sub. Specifically, we'll cover:

1. Publishing Messages: How to send notifications.
2. Subscribing to Channels: How to receive and handle notifications.

To receive notifications, we set up a subscriber that listens to a specific channel. In our implementation, this is handled by the JedisPubSub class, which processes incoming messages:

This setup listens for messages on a channel and unsubscribes after receiving a certain number of messages (maxMessages). The subscriber runs in a separate thread:

This thread subscribes to the "chat_room" channel and processes messages in real time.

To send notifications, we use the publishMessage method, which sends messages to the specified channel:

This method converts the Notification object to JSON format and publishes it to the channel.

In the Main class, we publish messages like this:

Messages are published to the "chat_room" channel, where the subscriber listens and processes them.

Here’s the full flow in action:

1. Start the subscriber in a separate thread to listen for messages on the "chat_room" channel.
2. Publish messages to the same channel.
3. Unsubscribe automatically after processing a set number of messages or manually after a timeout.

The output for this implementation will look like:

In this code, the JedisPubSub instance processes incoming messages in real time, and the publishMessage method allows you to send notifications. This combination forms the core of our Redis-based real-time notification system.

Exciting, isn’t it? Now, it's time to put this into practice. Let's implement the complete code to build our real-time notification system.

Happy coding!