Why does URL pattern /admin/* also match /admin - servlets

Question

I'm working with JBOSS AS 7 and I noticed an odd behavior, concerning servlet mapping.
My web.xml :
<context-param>
<param-name>APPLICATION_NAME</param-name>
<param-value>scom</param-value>
</context-param>
<servlet>
<servlet-name>admin</servlet-name>
<servlet-class>com.afp.iris.sr.sco.scom.servlet.ScomIHMServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>admin</servlet-name>
<url-pattern>/admin/*</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>Resteasy</servlet-name>
<servlet-class>org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher</servlet-class>
<init-param>
<param-name>resteasy.scan</param-name>
<param-value>true</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>Resteasy</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
<filter-mapping>
<filter-name>IrisFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<filter>
<filter-name>CAS Single Sign Out Filter</filter-name>
<filter-class>org.jasig.cas.client.session.SingleSignOutFilter</filter-class>
<init-param>
<param-name>artifactParameterName</param-name>
<param-value>SAMLart</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>CAS Single Sign Out Filter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<listener>
<listener-class>org.jasig.cas.client.session.SingleSignOutHttpSessionListener</listener-class>
</listener>
<filter>
<filter-name>CAS Authentication Filter</filter-name>
<filter-class>org.jasig.cas.client.authentication.Saml11AuthenticationFilter</filter-class>
<init-param>
<param-name>casServerLoginUrl</param-name>
<param-value>${cas.server.url.login}</param-value>
</init-param>
<init-param>
<param-name>serverName</param-name>
<param-value>${COMPONENT_HOST_URL}</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>CAS Authentication Filter</filter-name>
<url-pattern>/admin</url-pattern>
</filter-mapping>
<filter>
<filter-name>CAS Validation Filter</filter-name>
<filter-class>org.jasig.cas.client.validation.Saml11TicketValidationFilter</filter-class>
<init-param>
<param-name>casServerUrlPrefix</param-name>
<param-value>${cas.server.url.prefix}</param-value>
</init-param>
<init-param>
<param-name>serverName</param-name>
<param-value>${COMPONENT_HOST_URL}</param-value>
</init-param>
<init-param>
<param-name>redirectAfterValidation</param-name>
<param-value>true</param-value>
</init-param>
<init-param>
<param-name>useSession</param-name>
<param-value>true</param-value>
</init-param>
<init-param>
<param-name>acceptAnyProxy</param-name>
<param-value>true</param-value>
</init-param>
<init-param>
<param-name>tolerance</param-name>
<param-value>${cas.tolerance}</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>CAS Validation Filter</filter-name>
<url-pattern>/admin</url-pattern>
</filter-mapping>
<filter>
<filter-name>CAS HttpServletRequest Wrapper Filter</filter-name>
<filter-class>org.jasig.cas.client.util.HttpServletRequestWrapperFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>CAS HttpServletRequest Wrapper Filter</filter-name>
<url-pattern>/admin</url-pattern>
</filter-mapping>
<filter>
<filter-name>CAS Assertion Thread Local Filter</filter-name>
<filter-class>org.jasig.cas.client.util.AssertionThreadLocalFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>CAS Assertion Thread Local Filter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
When I tape the following URL /admin I get redirected to the cas server which is normal, after that I get redirected to ScomIHMServlet, and this is the part that I miss in all this process, /admin doesn't match /admin/* so how could this be achieved ? Sorry for the long web.xml file well i tried to post the most important parts of it, any suggestion would be apreciated.

Answer 1

You should interpret /admin as a folder.
If it were theoretically a file, then it indeed won't match.
If it were a folder, then you should interpret actual URL as /admin/. Surely this matches /admin/* as * means "zero or more characters".