If this is a JSTL1.1 version, use<%@ taglib prefix="C" uri="Http://java.sun.com/jsp/jstl/core"%>Otherwise, if it is a JSTL1.0 version, use the<%@ taglib prefix="C" uri="Http://java.sun.com/jstl/core"%>, you also need to import JSTL and standard two jar packages into your project.<c:choose>、<c:when>And<c:otherwise>The use of tags must conform to the following syntax rules:<c:when>And<c:otherwise>Cannot be used alone, they must be located in<c:choose>The parent tag. In<c:choose>The label can contain one or more<c:when>Label. In<c:choose>The label may not contain<c:otherwise>Label. In<c:choose>If the label contains both<c:when>And<c:otherwise>Label, then<c:otherwise>Must be located in<c:when>After the label. If you need to determine if an object in the session is not empty<c:when Test="${!empty session.user}">Similarly, if you want to judge the empty<c:when Test="${empty session.user}">
Jstl label <c:choose><c:when><c:otherwise> label