I had a similar issue.

I investigated it by editing the server8080.xml file to increase the debugging level from 0 to 2 everywhere I could see debug. I had to stop jbuilder to be able to save the server8080.xml file.

I eventually discovered that jbuilder was using its internal browser to make a request from the Tomcat that it started. The URL that the browser was asking for was simply /. It should have been asking for /appname, or even /appname/hello.jsp.

I fixed this by going to the Run Configurations page, and choosing Edit. The window that comes up has categories for: Server/Command Line, Server/Libraries, Services/JSP/Servlets, and Services/Naming/Directory. The JSP/Servlets has a checkbox that was checked and greyed out. But I clicked on the words JSP/Servlets to get the appropriate pane, where I could enter the Launch URI as /appname/hello.jsp.

(I expect that by adding a welcome-file in web.xml, I could have omitted the hello.jsp part.)

All fixed. Hope it helps someone else!

On Tomcat if you are deploying a war to the default app, and the name of your war is not the same as the name of your servlet, this happens. For example, if your web,xml looks like this:

  
    tunnel-test ...