<filter-name>SessionFilter</filter-name>

       <url-pattern>*.do</url-pattern>

</filter-mapping>

以上内容表示所以的请求中以.do结尾的都有首先通过我们这里指定的过滤器：

(3)Servlet来测试：

public class DownLoadDemo extends HttpServlet {

     private static final long serialVersionUID = 1L;

     public DownLoadDemo() {

        super();

    }

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

       this.doPost(request, response);

    }

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {