Connecting Java and JavaScript without Applets

Other Questions JavaScript
1

Hey everyone, I’m stuck with a problem in my project. I’ve got this Java code that’s not an Applet subclass, but it can still be called from a web page. The same code is used outside the browser too.

Now I need to send some data from Java to the JavaScript on the web page. Usually, I’d use JSObject for this, but it seems to only work with Applet subclasses.

Does anyone know if there’s a way to:

  1. Use JSObject without being an Applet subclass?
  2. Find another method to communicate with the JavaScript on the page?

I’d really appreciate any help or ideas. Thanks!

2

Have you considered using a server-side technology like Servlets or JavaServer Pages (JSP)? These can act as intermediaries between your Java code and the JavaScript on the web page. You could set up a Servlet that receives data from your Java application and then forwards it to the client-side JavaScript using AJAX or server-sent events. This approach doesn’t require Applets and works well for non-real-time communication. If you need real-time updates, WebSockets might be a better option as suggested earlier. They’re more complex to set up but offer bidirectional communication. Remember to handle any potential security concerns when exposing your Java functionality to the web.

3

I’ve faced a similar challenge in a project where we needed to bridge Java and JavaScript without Applets. We ended up using a combination of REST APIs and Server-Sent Events (SSE).

For sending data from Java to JavaScript, SSE worked brilliantly. We set up an SSE endpoint in our Java backend using Spring Boot. The JavaScript client then established a connection to this endpoint.

On the Java side, we used Spring’s SseEmitter to push updates. Something like:

@GetMapping("/sse")
public SseEmitter streamSSE() {
    SseEmitter emitter = new SseEmitter();
    // Logic to send events
    return emitter;
}

The JavaScript part was straightforward:

let eventSource = new EventSource('/sse');
eventSource.onmessage = event => {
    console.log(event.data);
};

This approach gave us real-time updates from Java to JavaScript without the complexity of WebSockets. For JavaScript to Java communication, we used simple REST endpoints. It worked seamlessly across browsers and didn’t require any special plugins or setups.

4

have u tried using websockets? they’re pretty good for this kinda thing. i used them in a project once and it worked great for sending data between java and js. no need for applets or anything. just set up a websocket server in java and connect to it from your javascript. its not too hard to set up