自定义 JSP 页面

发布于 2024-10-14 09:30:33 字数 1442 浏览 3 评论 0原文

根据用户会话，我必须在 JSP 上显示不同的内容。

有问题请指教

  <c:if test="${session.getAttribute("userEmail")}">

        <c:choose>
        <c:when test="[email protected]"> //here if test is not null
        <tr>
            <td colspan="1" width="40%" nowrap="nowrap" style="text-align: left;">
            <img src="<%=request.getContextPath()%>/images/icons/chevron_double.gif"/>
            <a href="http://www.google.com" class="underlinedLinksLic">Google</a>

            &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
            <img src="<%=request.getContextPath()%>/images/icons/chevron_double.gif"/>
            <a href="http://www.gmail.com" class="underlinedLinksLic">Gmail</a></td>  

        </tr>
        </c:when>
        <c:when test="[email protected]">   //here if session is null
        <tr>Hello</tr>  
        </c:when>

        <tr height="3px;">
            <td>&nbsp;</td>
        </tr>

    </c:choose>

原文

Based on the user session I have to display different stuff on JSP.

Something is wrong, please advice

  <c:if test="${session.getAttribute("userEmail")}">

        <c:choose>
        <c:when test="[email protected]"> //here if test is not null
        <tr>
            <td colspan="1" width="40%" nowrap="nowrap" style="text-align: left;">
            <img src="<%=request.getContextPath()%>/images/icons/chevron_double.gif"/>
            <a href="http://www.google.com" class="underlinedLinksLic">Google</a>

                        
            <img src="<%=request.getContextPath()%>/images/icons/chevron_double.gif"/>
            <a href="http://www.gmail.com" class="underlinedLinksLic">Gmail</a></td>  

        </tr>
        </c:when>
        <c:when test="[email protected]">   //here if session is null
        <tr>Hello</tr>  
        </c:when>

        <tr height="3px;">
            <td> </td>
        </tr>

    </c:choose>

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江湖正好 2024-10-21 09:30:33

<c:if test="${session.getAttribute("userEmail")}">

这是行不通的。这应该是

<c:if test="${not empty userEmail}">

只要作用域属性 userEmail 不是 null 或空字符串，就会输入块。要在 userEmail 属性为 null 或空字符串时显示一些内容，请执行以下操作：

<c:if test="${empty userEmail}">

此外，这些字符串比较

<c:when test="[email protected]">
<c:when test="[email protected]">

应该已经

<c:when test="${userEmail == '[email protected]'}">
<c:when test="${userEmail == '[email protected]'}">

了解了这些事实，您应该能够重构您的和块更合适。下面是一个示例：

<c:if test="${not empty userEmail}">
    This block will be displayed when attribute `userEmail` is not empty.

    <c:choose>
        <c:when test="${userEmail == '[email protected]'}">
            This block will be displayed when `userEmail` matches [email protected].
        </c:when>
        <c:when test="${userEmail == '[email protected]'}">  
            This block will be displayed when `userEmail` matches [email protected].
        </c:when>
        <c:otherwise>
            There must always be a `c:otherwise` block. 
            This will be displayed when attribute `userEmail` doesn't match anything.
        </c:otherwise>
    </c:choose>
</c:if>
<c:if test="${empty userEmail}">
    This block will be displayed when attribute `userEmail` is empty.
</c:if>

另请参阅：

<c:if test="${session.getAttribute("userEmail")}">

This ain't going to work. This should have been

<c:if test="${not empty userEmail}">

The <c:if> block will then be entered whenever the scoped attribute userEmail is not null or empty string. To show some stuff when the userEmail attribute is null or empty string, then do so:

<c:if test="${empty userEmail}">

Further, those String comparisons

<c:when test="[email protected]">
<c:when test="[email protected]">

should have been

<c:when test="${userEmail == '[email protected]'}">
<c:when test="${userEmail == '[email protected]'}">

Knowing those facts, you should be able to reconstruct your <c:if> and <c:choose> blocks more appropriately. Here's an example:

<c:if test="${not empty userEmail}">
    This block will be displayed when attribute `userEmail` is not empty.

    <c:choose>
        <c:when test="${userEmail == '[email protected]'}">
            This block will be displayed when `userEmail` matches [email protected].
        </c:when>
        <c:when test="${userEmail == '[email protected]'}">  
            This block will be displayed when `userEmail` matches [email protected].
        </c:when>
        <c:otherwise>
            There must always be a `c:otherwise` block. 
            This will be displayed when attribute `userEmail` doesn't match anything.
        </c:otherwise>
    </c:choose>
</c:if>
<c:if test="${empty userEmail}">
    This block will be displayed when attribute `userEmail` is empty.
</c:if>