One common question you might have at this stage is "why don't I just do a find and replace for javax to jakarta?" The answer is that not all javax packages have been migrated to the jakarta namespace. For example, javax.transaction.xa package is not using Jakarta.

We're going to use IntelliJ IDEA's migration tool for the next steps. From the menu, navigate to Refactor | Migrate Packages and Classes | Java EE to Jakarta EE.

You can select the scope here, for example MyWebApp. This also allows you to go module by module if you’re working with a larger, more realistic application. Press Run to get a preview of the refactorings.

Press Refactor. Your Java classes should be fixed now and not showing any errors. Now let's rebuild our application with ⌘F9 (macOS) / Ctrl+F9 (Windows/Linux) and then run it with ⌃R (macOS) / Shift+F10 (Windows/Linux).

Now you should be able to navigate to localhost:8080/MyWebApp again and see the application running once more without any errors.