Illegal use of <when>-style tag without <choose> as its direct parent
这个错误一般是在jsp页面中非法使用<when>标签 该标签必须是<choose>标签的直接子标签 不能单独是<when>标签
下面给出一个例子
<c:choose>
<c:when test="testCondition">
Content1
</c:when>
<c:when test="testCondition">
Content2
</c:when>
<c:otherwise>
Content3
</c:otherwise>
</c:choose>