jstl if else的使用 及多项选择
结构：
<c:choose>
<c:when test=""> 如果
</c:when>
<c:otherwise> 否则
</c:otherwise>
</c:choose>
<c:if test="${!empty categoryId}">
<c:choose>
<c:when test="${categoryId == 1"><dt>下载类游戏</dt></c:when>
<c:when test="${categoryId == 2"><dt>下载类应用</dt></c:when>
<c:when test="${categoryId == 3"><dt>网页游戏</dt></c:when>
</c:choose>
</c:if>
