Normally this should work with a glassfish-web.xml
looking like this:
<!DOCTYPE glassfish-web-app PUBLIC
"-//GlassFish.org//DTD GlassFish Application Server 3.1 Servlet 3.0//EN"
"http://glassfish.org/dtds/glassfish-web-app_3_0-1.dtd">
<glassfish-web-app>
<context-root>/path/to/App</context-root>
</glassfish-web-app>
But here it looks like you need a file called sun-web.xml
for your task.
Here is an example:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE sun-web-app PUBLIC
"-//Sun Microsystems, Inc.//DTD GlassFish Application Server 3.0 Servlet 3.0//EN"
"http://www.sun.com/software/appserver/dtds/sun-web-app_3_0-0.dtd">
<sun-web-app error-url="">
<context-root>/path/to/our/App</context-root>
</sun-web-app>