在jsp页面中不能通过${list.size}取列表长度，而是
<%@ taglib uri="<a target=_blank style="color: rgb(51, 102, 153); text-decoration: none;" href="http://java.sun.com/jsp/jstl/core" target="_blank" rel="nofollow">http://java.sun.com/jsp/jstl/core</a>" prefix="c"%>
<%@ taglib prefix="fn" uri="<a target=_blank style="color: rgb(51, 102, 153); text-decoration: none;" href="http://java.sun.com/jsp/jstl/functions" target="_blank" rel="nofollow">http://java.sun.com/jsp/jstl/functions</a>"%>
list的长度是：${fn:length(list)}