web.xmlへのservlet定義

Java Servlet 
<servlet>
  <servlet-name>servletName</servlet-name>
  <servlet-class>packageName.ClassFileName</servlet-class>
</servlet>
<servlet-mapping>
  <servlet-name>servletName</servlet-name>
  <url-pattern>/actionName</url-pattern>
</servlet-mapping>

呼び出し例

jsp

<form action="/contextPath/actionName" method="GET">
 <input type="submit" value="GO" /> 
</form>

Servlet

req.getServletContext().getRequestDispatcher(actionName).forward(req, res);

URLダイレクトアクセス

http://host:port/contextPath/actionName