jsp页面不显示表列标题

Question

我目前正在制作一个有8列的表格。首先，我检查值是否为null，如果不为null，我会写出列的列标题（例如：“名字：”）。接下来，我遍历一个列表，并使用适当的值填充每个列（如果它不为null）。我的问题是，当表中的实际数据打印时，列标题（在下面的代码中的注释之间）不会打印。任何人都可以帮助我吗？

<table style="width: 100%">
    <c:choose>
        <c:when test="${empty serviceRequests}">
        </c:when>
        <c:otherwise>
            <tr>                    //DOES NOT PRINT STARTING FROM HERE
                <td><c:choose>
                        <c:when test="${empty serviceRequestData['ID']}"></c:when>
                        <c:otherwise>
                            <u>ID:</u>
                        </c:otherwise>
                    </c:choose></td>
                <td><c:choose>
                        <c:when test="${empty serviceRequestData['FN_Contact']}"></c:when>
                        <c:otherwise>
                            <u>First Name:</u>
                        </c:otherwise>
                    </c:choose></td>
                <td><c:choose>
                        <c:when test="${empty serviceRequestData['LN_Contact']}"></c:when>
                        <c:otherwise>
                            <u>Last Name:</u>
                        </c:otherwise>
                    </c:choose></td>
                <td><c:choose>
                        <c:when test="${empty serviceRequestData['Email']}"></c:when>
                        <c:otherwise>
                            <u>Email:</u>
                        </c:otherwise>
                    </c:choose></td>
                <td><c:choose>
                        <c:when test="${empty serviceRequestData['FN_Reporter']}"></c:when>
                        <c:otherwise>
                            <u>Reporter First Name:</u>
                        </c:otherwise>
                    </c:choose></td>
                <td><c:choose>
                        <c:when test="${empty serviceRequestData['LN_Reporter']}"></c:when>
                        <c:otherwise>
                            <u>Reporter Last Name:</u>
                        </c:otherwise>
                    </c:choose></td>
                <td><c:choose>
                        <c:when test="${empty serviceRequestData['Company']}"></c:when>
                        <c:otherwise>
                            <u>Company:</u>
                        </c:otherwise>
                    </c:choose></td>
                <td><c:choose>
                        <c:when test="${empty serviceRequestData['Notes']}"></c:when>
                        <c:otherwise>
                            <u>Notes:</u>
                        </c:otherwise>
                    </c:choose></td>
            </tr>                                 //DOES NOT PRINT ENDING HERE
            <c:forEach var="serviceRequestData" items="${serviceRequests}">
                <tr>
                    <td><c:choose>
                            <c:when test="${empty serviceRequestData['ID']}">
                            Null
                        </c:when>
                            <c:otherwise>
                            ${serviceRequestData['ID']}
                        </c:otherwise>
                        </c:choose></td>
                    <td><c:choose>
                            <c:when test="${empty serviceRequestData['FN_Contact']}">
                            Null
                        </c:when>
                            <c:otherwise>
                            ${serviceRequestData['FN_Contact']}
                        </c:otherwise>
                        </c:choose></td>
                    <td><c:choose>
                            <c:when test="${empty serviceRequestData['LN_Contact']}">
                            Null
                        </c:when>
                            <c:otherwise>
                            ${serviceRequestData['LN_Contact']}
                        </c:otherwise>
                        </c:choose></td>
                    <td><c:choose>
                            <c:when test="${empty serviceRequestData['Email']}">
                            Null
                        </c:when>
                            <c:otherwise>
                            ${serviceRequestData['Email']}
                        </c:otherwise>
                        </c:choose></td>

                    <td><c:choose>
                            <c:when test="${empty serviceRequestData['FN_Reporter']}">
                            Null
                        </c:when>
                            <c:otherwise>
                            ${serviceRequestData['FN_Reporter']}
                        </c:otherwise>
                        </c:choose></td>
                    <td><c:choose>
                            <c:when test="${empty serviceRequestData['LN_Reporter']}">
                            Null
                        </c:when>
                            <c:otherwise>
                            ${serviceRequestData['LN_Reporter']}
                        </c:otherwise>
                        </c:choose></td>
                    <td><c:choose>
                            <c:when test="${empty serviceRequestData['Company']}">
                            Null
                        </c:when>
                            <c:otherwise>
                            ${serviceRequestData['Company']}
                        </c:otherwise>
                        </c:choose></td>

                    <td><c:choose>
                            <c:when test="${empty serviceRequestData['Notes']}">
                            Null
                        </c:when>
                            <c:otherwise>
                            ${serviceRequestData['Notes']}
                        </c:otherwise>
                        </c:choose></td>

                </tr>
            </c:forEach>
        </c:otherwise>
    </c:choose>
</table>

Answer 1

在用于迭代数据行的<c:forEach>之前，不会定义您在表头中尝试访问的变量。

这应该有效：

<table style="width: 100%">
  <c:choose>
    <c:when test="${empty serviceRequests}"></c:when>
    <c:otherwise>
      <tr>
        <td>
          <u>ID:</u>
        </td>
        <td>
          <u>First Name:</u>
        </td>
        <td>
          <u>Last Name:</u>
        </td>
        <td>
          <u>Email:</u>
        </td>
        <td>
          <u>Reporter First Name:</u>
        </td>
        <td>
          <u>Reporter Last Name:</u>
        </td>
        <td>
          <u>Company:</u>
        </td>
        <td>
          <u>Notes:</u>
        </td>
      </tr>
      <c:forEach var="serviceRequestData" items="${serviceRequests}">
        ...
      </c:forEach>
    </c:otherwise>
  </c:choose>
</table>

当然，您需要弄清楚要用于包装标头值的逻辑（如果有的话）。