I think you missed the servlet-mapping part in your web.xml.

Your web.xml should be something like this:

<web-app>
<servlet>
   <servlet-name>name</servlet-name>
   <servlet-class>hello</servlet-class>
</servlet>
<servlet-mapping>
        <servlet-name>name</servlet-name>
        <url-pattern>/heloo</url-pattern>
</servlet-mapping>
</web-app>