App Engine项目中生成的Servlet配置web.xml

Question

我对eclipse中我的app引擎项目中web.xml中生成的servlet配置感到好奇。这是为了什么目的：

<servlet>
    <servlet-name>SystemServiceServlet</servlet-name>
        <servlet-class>com.google.api.server.spi.SystemServiceServlet</servlet-class>
        <init-param>
            <param-name>services</param-name>
            <param-value/>
        </init-param>
</servlet>

<servlet-mapping>
    <servlet-name>SystemServiceServlet</servlet-name>
    <url-pattern>/_ah/spi/*</url-pattern>
</servlet-mapping>