Searching the console for cause by found the following statement: The servlets .. are both mapped to the url-pattern [/IndexServlet] which is not permitted
The solution is to delete the web.xml file. Or delete @webServlet
reason:
The new version of eclipse will not generate web.xml by itself, nor does it need to configure the xml file by itself.
Eclipse already has another good solution: using @WebServlet annotation
So you configured this repeatedly.
It took a long time. . . .