Wouldn't the URL be
{{WARName}}/Hello
This is always the place where everyone gets confused. I still do after years and years.
If you deploy on
Tomcat or an App Server it typically maps the URL to the war file name unless you set it somewhere else.
Then you have to add the
Servlet mapping, which in your case is just "/"
Then you add the RequestMapping which you have at the class level and is set to "/Hello"
Which if the war was called "mark.war" the the URL would be
localhost:8080/mark/Hello
Mark