It is a bit of a challenge to get GWT to work well in IntelliJ with Jetty. We finally got it working very well a year ago, thanks to a site that explained some of the key points for getting it to work. The URL of the site is
https://imsavva.com/how-to-debug-gwt-in-2021-and-fix-error-scanning-entry/
The site is a bit dated, but the main points are still valid. If you use jetty, do use jetty 10, not jetty 11. GWT 2.10.0 works. Java versions all the way to java 17 work. Not sure whether jetty 9.4 works with Java 9 and up; we never tried that combination. Over the last year, our combinations, with IntelliJ, have been:
1. gwt 2.8.2 with builtin jetty 9.2 (initially, before we moved to using the jetty plugin in IntelliJ))
2. gwt 2.8.2, gwt 2.9.0, and gwt 2.10.0 with jetty plugin (jetty 9.4) and java 8
3. gwt 2.10 with jetty 10 and jetty plugin and java 17. This is what we have now. The GWT configuration is a tiny bit different as GWT 2.10.0 can only handle Java 11 right now, not Java 17.
We never found the need to use the jetty plugin until we needed to use WebSocket and jetty 9.2 can't handle WebSocket very well. There was a way to get around it, but unfortunately that way was blocked by Java 9 and up. A year ago, I found out about that site. I followed the instructions from that site and got everything working with some changes, as my source code structure is different from his.
Let me know if you encountered an issue you can't solve. I don't check the mailbox of this email address, so posting the questions here is better. If this is the right way to go about this in this group.
We have been using GWT since the beginning, for almost 15 years now. We started using jetty about 8 years ago; before that, we were using Tomcat (and Apache). We migrated from Eclipse to IntelliJ about 3 years ago. We never use maven as we need to be able to build the whole system with everything included in a repo (except Java). Just a weird requirement, that is for sure. So, we are still using ant to build our war file as well.