Evo jednog primera web.xml za aplikaciju kreiranu u Spring frameworku. Mislim da ce ti biti jasnije.

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<display-name>training</display-name>

<!-- Servlet configuration -->
<servlet>
<servlet-name>training</servlet-name>
<servlet-class>
org.springframework.web.servlet.DispatcherServlet
</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>

<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>


<!-- Context Configuration -->
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/classes/training-data.xml, /WEB-INF/classes/training-services.xml, /WEB-INF/classes/training-acegi.xml</param-value>
</context-param>

<listener>
<listener-class>
org.springframework.web.context.ContextLoaderListener
</listener-class>
</listener>


<servlet-mapping>
<servlet-name>training</servlet-name>
<url-pattern>*.htm</url-pattern>
</servlet-mapping>

<!-- Welcom file list -->
<welcome-file-list>
<welcome-file>index.htm</welcome-file>
</welcome-file-list>

<!-- Filter Chain Proxy Configuration -->
<filter>
<filter-name>filterChainProxy</filter-name>
<filter-class>org.acegisecurity.util.FilterToBeanProxy</filter-class>
<init-param>
<param-name>targetBean</param-name>
<param-value>filterChainProxy</param-value>
</init-param>
</filter>

<filter-mapping>
<filter-name>filterChainProxy</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

<!-- Error page -->
<error-page>
<exception-type>java.lang.Exception</exception-type>
<location>/error.jsp</location>
</error-page>

<!-- Tag Lib Configuration -->
<jsp-config>
<taglib>
<taglib-uri>/WEB-INF/tlds/c.tld</taglib-uri>
<taglib-location>/WEB-INF/tlds/c.tld</taglib-location>
</taglib>
</jsp-config>



</web-app>

Ukoliko koristis neki IDE sa podrskom za J2EE, on ce ti automatski generisati ovaj fajl, pa mozes i tako da vidis..

Iskoristi onaj koji je dat kao primer u webapps/WEB-INF folderu. Naći ćeš ga u matičnom folderu gde si instalirao tomcat. Na Windowsu je to uobičajeno "Program FilesApache Software FoundationTomcat <verzija>". U svakom slučaju, za osnovnu upotrebu su ti dovoljni tagovi <servlet> i <servlet-mapping>. Imaš detaljno sve objašnjeno u Tomcatovoj dokumentaciji.

Napravio sam Web.xml fajl ali i dalje ne mogu da pokrenem servlet!
ne moze da ga nadje 404.
nikako ne mogu da ga otvorim. sta sve treba da odradim pre toga, startovao sam tomcat, uvukao sam servlet-api.jar....