我在jsp里面使用c标签做判断的时候，billStatus是有值的，但是就是不进c:when直接走c:otherwise.这到底是什么原因？

<c:choose>
<c:when test="${order.billStatus=='0'}">待付款</c:when>
<c:when test="${order.billStatus=='1'}">已付款</c:when>
<c:when test="${order.billStatus=='2'}">已退款</c:when>
<c:when test="${order.billStatus=='3'}">订单完成</c:when>
<c:when test="${order.billStatus=='4'}">已删除订单</c:when>
<c:when test="${order.billStatus=='5'}">退单</c:when>
<c:when test="${order.billStatus=='6'}">回单</c:when>
<c:when test="${order.billStatus=='7'}">支付失败</c:when>
<c:otherwise>异常</c:otherwise>
</c:choose>