Spring boot websocket push notification application

Step 1: Create a new Spring Boot Project To create a new Spring Boot project, go to https://start.spring.io/ and set the project metadata as per your requirement. Also, add the Websocket dependency to your project.

Step 2: Create a WebSocket Configuration Class Create a WebSocket configuration class that extends the AbstractWebSocketMessageBrokerConfigurer class. Add the @EnableWebSocketMessageBroker annotation to the class.

Step 3: Configure WebSocket Endpoints Configure the WebSocket endpoints using the registerStompEndpoints() method in the configuration class. This method registers the endpoint that clients use to connect to the WebSocket server.

Step 4: Configure Message Broker Configure the message broker using the configureMessageBroker() method in the configuration class. The message broker is responsible for routing messages from the server to clients.

Step 5: Create a Controller Create a controller class to handle WebSocket messages. This class should contain methods annotated with @MessageMapping to handle messages received from clients.

Step 6: Implement a Notification Service Implement a notification service that will be used to send notifications to clients over WebSocket.

Step 7: Connect to the WebSocket server In your client-side code, connect to the WebSocket server using the SockJS and Stomp libraries.

With these steps, you will have created a Spring Boot WebSocket push notification application. Here's some sample code to help you get started:

WebSocketConfig.java:

@Configuration
@EnableWebSocketMessageBroker
public class WebSocketConfig extends AbstractWebSocketMessageBrokerConfigurer {

    @Override
    public void registerStompEndpoints(StompEndpointRegistry registry) {
        registry.addEndpoint("/ws").withSockJS();
    }

    @Override
    public void configureMessageBroker(MessageBrokerRegistry config) {
        config.enableSimpleBroker("/topic");
        config.setApplicationDestinationPrefixes("/app");
    }
}

This class enables the simple message broker and sets the application destination prefix. It also registers a STOMP WebSocket endpoint with SockJS fallback.

NotificationController.java:

@Controller
public class NotificationController {

    @Autowired
    private NotificationService notificationService;

    @MessageMapping("/notifications")
    @SendTo("/topic/notifications")
    public Notification sendNotification(Notification notification) {
        notificationService.sendNotification(notification);
        return notification;
    }
}

NotificationService.java:

@Service
public class NotificationService {

    @Autowired
    private SimpMessagingTemplate messagingTemplate;

    public void sendNotification(Notification notification) {
        messagingTemplate.convertAndSend("/topic/notifications", notification);
    }
}

This class uses the SimpMessagingTemplate to send notifications to the /topic/notifications destination.

Finally, create a Notification class that represents a notification:

Notification.java:

public class Notification {

    private String message;

    public Notification() {
    }

    public Notification(String message) {
        this.message = message;
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }
}

That's it! With these classes, you can now send notifications to clients using the WebSocket endpoint. To receive notifications, clients can subscribe to the /topic/notifications destination using the following JavaScript code:

var socket = new SockJS('/websocket');
var stompClient = Stomp.over(socket);

stompClient.connect({}, function(frame) {
    stompClient.subscribe('/topic/notifications', function(notification) {
        // handle the notification here
    });
});

This code creates a SockJS WebSocket connection and subscribes to the /topic/notifications destination. When a notification is received, the code can handle it as desired.