Make sure the icon is served, i.e. make a request to /favicon.ico and see if it renders.
If it does, add this to your web.xml to make sure Tomcat sends the correct Content-Type
with the response:
<mime-mapping>
<extension>ico</extension>
<mime-type>image/x-icon</mime-type>
</mime-mapping>
Make sure <mvc:default-servlet-handler />
is present if you map the dispatcher servlet to /
.