错误：
String realPath = " http:// " + request.getServerName() + " : " + request.getServerPort() + request.getContextPath();
String realPath = " http:// " + request.getServerName() + " : " + request.getServerPort() + request.getServletPath();
正确：
String realPath = " http:// " + request.getServerName() + " : " + request.getServerPort() + request.getContextPath() + request.getServletPath().substring( 0 ,request.getServletPath().lastIndexOf( " / " ) + 1 );
如果想连带获取页面的名称时则去掉最后的substring即可.
（1）利用<jsp:param name="paramName" value="paramValue"></jsp:param>其中name为与属性相关联的关键词，value为属性的值。
示例：传常量字符串<param name="userName" value="shilei"/>
示例：传变量 User user=new User("shilei");//User是一个类
&n ......
