el 表达式中某一项过长时需要截取字符串长度，当悬停的时候显示全部内容

首先需要引入红色的标签

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn" %>
         
<table border="1" cellpadding="0" cellspacing="0" width="85%">
        <tr>
            <td>客户姓名</td>
            <td>性别</td>
            <td>生日</td>
            <td>手机</td>
            <td>邮箱</td>
            <td>爱好</td>
            <td>类型</td>
            <td>备注</td>
            <td>操作</td>
        <tr>
        <c:forEach var="c" items="${requestScope.list }">
            <tr>
                <td>${c.name }</td>
                <td>${c.gender }</td>
                <td>${c.birthday }</td>
                <td>${c.cellphone }</td>
                <td>${c.email }</td>
                <td>${c.preference }</td>
                <td>${c.type }</td>
                <td title="${c.description}" >     //当鼠标悬停时显示其全部内容  a标签也有title这个属性
                   <c:if test="${fn:length(c.description)>12 }">
                         ${fn:substring(c.description, 0, 12)}...
                   </c:if>
                  <c:if test="${fn:length(c.description)<=12 }">
                         ${c.description }
                   </c:if>
                </td>
                <td>
                    <a href="#">修改</a>
                    <a href="#">刪除</a>
                </td>
            </tr>
        </c:forEach>
     </table>