Error when serving the basic "Type your name here" demo application.

When trying to serve the basic starting Maven app from a WAR file (the one that gives the message “Type your name here” and then has a button “Click Me”), the GUI only shows a loading graphic and gives the following error on the client side browser:

Uncaught SyntaxError: Unexpected token G in JSON at position 0
at JSON.parse ()
at XMLHttpRequest.r.onreadystatechange (vaadinBootstrap.js?v=8.1.6:168)

I’m not sure how to proceed in trying to figure out what is going wrong and wonder if anyone has experience with this issue.

The server is IIS with Tomcat.

It looks like you have a problem with IIS settings. Some requests are not being forward from server (Tomcat) to browser in correct way, thus you get this exception.