when tomcat know "*" as "any"?

[zb cong]

hello
my "web.xml" as follow:


<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE web-app
PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN"
"http://java.sun.com/j2ee/dtds/web-app_2.2.dtd">
<web-app>
<servlet>
<servlet-name>freak</servlet-name>
<servlet-class>FreakServlet</servlet-class>
<init-param>
<param-name>waitInterval</param-name>
<param-value>5</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>freak</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping>
</web-app>

i confuse with the "url-pattern" tag,when i special "*.do",in the browser,"http://localhost:8080/freak/a.do" works well.
if "/*.do",then "http://localhost:8080/freak/a.do" don't work(page not found),but "http://localhost:8080/freak/*.do" works.
if "/*",all of them works.and you can cancatenate any string to "http://localhost:8080/freak/".

i wonder when the tomcat know the "*" as "any".
thanks in advance!