编译时xml文件总是出错

[MobiusStrip]

代码如下：求高人解答
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
</web-app>
<?xml version="1.0" encoding="UTF-8"?>
<!-- 网站登陆功能 -->
<servlet>
<description>
</description>
<display-name>UserLoginServlet</display-name>
<servlet-name>UserLoginServlet</servlet-name>
<servlet-class>ch12.servlet.UserLoginServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>UserLoginServlet</servlet-name>
<url-pattern>/UserLoginServlet</url-pattern>
</servlet-mapping>

[MobiusStrip]

修改后，出现404； The requested resource is not available. <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> <?xml version="1.0" encoding="UTF-8"?> <!-- 网站登陆功能 --> <servlet> <description> </description> <display-name>UserLoginServlet</display-name> <servlet-name>UserLoginServlet</servlet-name> <servlet-class>ch12.servlet.UserLoginServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>UserLoginServlet</servlet-name> <url-pattern>/UserLoginServlet</url-pattern> </servlet-mapping> </web-app>