j_security_check Not Available

I tried setting up security filter in Tomcat 4.1.18.  I created my own 
class which extends RealmBase.  I setup my web.xml and security-filter.xml 
files much like the files from the catalina example.  But when I try to 
login using  a form on my login page with the method set to POST and the 
action set to j_security_check, I get an error saying the requested 
resource j_security_check is unavailable.  I must be missing something. 
Could someone point me in the right direction?
Thanks.

Mark Lenz
Pierce Manufacturing, Inc.
(920) 832-3523
[email protected]


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Thank you.