Question

I have a servlet in tomcat. It takes a really long time for the java code in the backend to execute. Is there a way to load static resources (css,images,javascript) in parallel with the code in the backend? Right now, they are only loaded once the code finishes running.

Answer 1

You could use an Ajax-style solution where you paint your page without data, with a placeholder for retrieving the data, maybe even with a “loading” spinner graphic.

The way that an Ajax call works, when the page is loaded, some Javascript will fire that will launch an Ajax request to Tomcat via XmlHttpRequest that will start the calculation. The browser will notify the browser when the tomcat request is completed. Then there will be some javascript in the webpage that will take the response and replace the placeholder. If the server returns an HTML fragment, it’s as simple as executing in javascript placeholder-div.innerHtml = your-response-text.

Here’s a basic tutorial on Ajax and a Java-based example that has the web front-end communicating with a Java Servlet back-end.