How do you implement a WebSocket chat application with Spring Boot?

Table of Contents

Introduction

A WebSocket-based chat application allows real-time, two-way communication between the client and server. In this guide, we'll demonstrate how to implement a simple WebSocket chat application using Spring Boot and Spring WebSocket. We'll cover setting up the WebSocket configuration, handling messages, broadcasting to users, and handling WebSocket events like connection establishment and disconnection.

Step 1: Add Dependencies

To get started, you need to include the necessary dependencies in your pom.xml for WebSocket support.

Step 2: Configure WebSocket in Spring Boot

Create a WebSocket configuration class to enable WebSocket support in your Spring Boot application.

WebSocketConfig.java

In this configuration:

  • /chat is the WebSocket endpoint where clients will connect.
  • ChatWebSocketHandler is the handler that processes messages and manages the WebSocket communication.

Step 3: Create a WebSocket Message Handler

The ChatWebSocketHandler will manage incoming WebSocket messages and broadcast them to other connected users.

ChatWebSocketHandler.java

In this handler:

  • sessions: A set of active WebSocket sessions (clients).
  • afterConnectionEstablished(): Adds the session to the set when a new WebSocket connection is established.
  • handleTextMessage(): Broadcasts the incoming message to all connected users.
  • afterConnectionClosed(): Removes the session from the set when the connection is closed.

Step 4: Create a Simple HTML Frontend

Create an HTML page where users can send and receive chat messages via WebSocket. This will be served by Spring Boot.

src/main/resources/static/chat.html

This HTML page:

  • Creates a WebSocket connection to the Spring Boot server at /chat.
  • Displays received messages in the #chat div.
  • Sends messages to the WebSocket server when the "Send" button is clicked.

Step 5: Running the Application

Now, with the above components in place, you can run the Spring Boot application by executing:

Navigate to http://localhost:8080/chat.html in your browser. Open multiple tabs or different browsers to test the chat application. When a user sends a message, it will be broadcasted to all connected users in real-time.

Step 6: Enhancements (Optional)

1. User Identification:

You can implement user authentication by adding user information (e.g., username) to the WebSocket session and broadcasting the sender's name with each message.

2. Message Formatting:

Format the messages to make them visually distinguishable by including user names and timestamps in the message payload.

3. Private Messaging:

Enhance the chat app by implementing a private messaging feature using message selectors or custom routing.

4. Message Persistence:

Use a database or in-memory store like Redis to persist chat messages, ensuring the chat history is available for new users.

Conclusion

In this guide, we implemented a simple WebSocket chat application using Spring Boot. This involved configuring WebSocket support, handling messages, and broadcasting them to connected users in real-time. The architecture uses Spring WebSocket to establish connections, send messages, and manage sessions effectively. By expanding on this basic setup, you can create more complex chat applications with user management, message persistence, and even private messaging features.

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