<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn"%>--------這裏就需要有standard.jar這個包
引入兩個標籤庫之後就能實現長度判斷了,例如
<c:choose>
<c:when test="${fn:length(contact.tagschosen) == 0}">
<span class="grouped">未分組</span>
</c:when>
<c:otherwise>
<c:forEach items="${contact.tagschosen}" var="tags">
<span class="grouped">${tags.tagname}</span>
</c:forEach>
</c:otherwise>
</c:choose>