web.xml + jsf 2.2 + web servlet 3.1

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    version="3.0">

    <display-name>PrimeFaces HelloWorld Example</display-name>

    <!-- Define the JSF listener class when using the Jetty Maven Plugin 
        with Jetty8 -->
    <listener>
        <listener-class>com.sun.faces.config.ConfigureListener</listener-class>
    </listener>

    <welcome-file-list>
        <welcome-file>index.xhtml</welcome-file>
    </welcome-file-list>

    <servlet>
        <servlet-name>faces</servlet-name>
        <servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>faces</servlet-name>
        <url-pattern>*.jsf</url-pattern>
        <url-pattern>*.xhtml</url-pattern>
    </servlet-mapping>
</web-app>