How to reload webapp automaticly under tomcat 6.0.20

[red phoenix]

I set following statement in conf/server.xml, it can run well before
tomcat6.0.20,when I modify class file,tomcat can reload automaticly.
<Context path="/Test" docBase="Test" reloadable="true"
crossContext="true"></Context>

But when I use tomcat 6.0.2,I find it can't reload automaticly,why? Where is
wrong? How to do it?

Thanks