Implementing real-time notifications and alerts in Apache Wicket

25 Sep 2023

In today’s fast-paced world, users expect real-time updates and notifications from their applications. Apache Wicket, a popular Java web framework, provides a robust platform for building web applications with interactive features. In this blog post, we will explore how to implement real-time notifications and alerts using Apache Wicket.

Prerequisites

Before we dive into the implementation, make sure you have the following prerequisites:

Java JDK (version 8 or higher)
Apache Wicket (version 8.x or higher)
WebSocket API (Java API for WebSocket, included in Java EE 7 or higher)

Setting up WebSocket in Apache Wicket

To enable real-time communication between the server and the client, we need to configure WebSocket in Apache Wicket. Follow these steps to set up WebSocket in your application:

Add the following dependencies to your Maven pom.xml file:

<dependency>
    <groupId>org.apache.wicket</groupId>
    <artifactId>wicket-native-websocket-core</artifactId>
    <version>8.x.x</version>
</dependency>
<dependency>
    <groupId>javax.websocket</groupId>
    <artifactId>javax.websocket-api</artifactId>
    <version>1.1</version>
</dependency>

Create a new Wicket WebSocketApplication class that extends WebApplication:

public class MyWebSocketApplication extends WebApplication {

    @Override
    public void init() {
        super.init();

        // Enable WebSocket behavior
        getWebSocketSettings().setWebSocketFactory(new Jetty9WebSocketFactory());
    }

    @Override
    public Class<? extends Page> getHomePage() {
        return HomePage.class;
    }
}

Customize your web.xml file to use the WebSocketServletContainerInitializer:

<servlet>
    <servlet-name>ws</servlet-name>
    <servlet-class>org.apache.wicket.protocol.ws.jetty9.Jetty9WebSocketServletContainerInitializer</servlet-class>
</servlet>

<servlet-mapping>
    <servlet-name>ws</servlet-name>
    <url-pattern>/ws/*</url-pattern>
</servlet-mapping>

Implementing Real-Time Notifications

Now that we have set up WebSocket in Apache Wicket, let’s implement real-time notifications. Here’s an example scenario where we want to show a notification to the user whenever a new message is received:

Create a WebSocket behavior class:

public class NotificationWebSocketBehavior extends AbstractWebSocketBehavior {

    @Override
    protected void onMessage(WebSocketRequestHandler handler, TextMessage message) {
        // Process incoming message
        String notification = message.getText();
        
        // Create a notification panel and add it to the page
        NotificationPanel panel = new NotificationPanel("notification", Model.of(notification));
        handler.addComponent(panel);
        handler.push();
    }
    
    @Override
    public void renderHead(Component component, IHeaderResponse response) {
        super.renderHead(component, response);
        
        // Add JavaScript code to establish WebSocket connection
        String js = "var socket = new WebSocket('ws://localhost:8080/ws');";
        response.render(OnDomReadyHeaderItem.forScript(js));
    }
}

Attach the WebSocket behavior to a Wicket component:

public class HomePage extends WebPage {

    public HomePage() {
        // Create a form and add it to the page
        Form<Void> form = new Form<>("form");
        
        // Create a text field for message input
        TextField<String> messageField = new TextField<>("message", Model.of(""));
        form.add(messageField);
        
        // Create a submit button
        Button submitButton = new Button("submit") {
            @Override
            public void onSubmit() {
                // Send the message to the server
                WebSocketRequestHandler handler = new WebSocketRequestHandler(getPage());
                handler.push("New message: " + messageField.getModelObject());
                
                // Reset the input field
                messageField.setModelObject("");
                handler.add(messageField);
                handler.push();
            }
        };
        form.add(submitButton);
        
        // Attach the WebSocket behavior to the form
        form.add(new NotificationWebSocketBehavior());
        
        add(form);
    }
}

Conclusion

Implementing real-time notifications and alerts in Apache Wicket is a powerful way to enhance user experience in your web applications. With WebSocket support, you can easily establish a bidirectional communication channel between the server and the client, enabling real-time updates without the need for constant page refreshing.

By following the steps outlined in this blog post, you should now be able to implement real-time notifications and alerts in your Apache Wicket applications. Happy coding!

Prerequisites

Setting up WebSocket in Apache Wicket

Implementing Real-Time Notifications

Conclusion

#ApacheWicket #RealTimeNotifications