Illegal use of <when>-style tag without <choose> as its direct parent

Exception Name: org.apache.jasper.JasperException: javax.servlet.ServletException: javax.servlet.jsp.JspTagException: Illegal use of <when>-style tag without <choose> as its direct parent

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Exception Details: org.apache.jasper.JasperException: javax.servlet.ServletException: javax.servlet.jsp.JspTagException: Illegal use of <when>-style tag without <choose> as its direct parent at 

看看你是否漏了<c:choose></c:choose>标签

<c:when></c:when>需要嵌套在<c:choose></c:choose>标签中

或者可以选择直接使用<c:if></c:if>标签

<c:choose>
<c:when test="<boolean>">
...
</c:when>
<c:when test="<boolean>">
...
</c:when>
...
...
<c:otherwise>
...
</c:otherwise>
</c:choose>

http://www.runoob.com/jsp/jstl-core-choose-tag.html