在 JSP 中包含/导入文件之前，如何检查文件是否存在? [英] How can you check if a file exists before including/importing it in JSP?

问题描述

假设 requestScope.importMe 需要一个 JSP 文件的路径

Assuming that requestScope.importMe is expecting a path to a JSP file

<c:choose>
    <c:when test="${!empty requestScope.importMe && fileExists(requestScope.importMe) }">
    <c:import url="${requestScope.importMe}" />   
    ...
</c:choose>

如何在尝试包含文件之前检查文件是否存在，以免引发错误?

How can I check if the file exists before trying to include it so that an error is not thrown?

我更喜欢使用 JSTL 标签的解决方案.

I'd prefer a solution using JSTL tags.

推荐答案

放在 c:catch 标签.它将捕获任何抛出的 Exception 给你.

Put it in a c:catch tag. It will catch any thrown Exception for you.

<c:catch var="e">
    <c:import url="${url}" />
</c:catch>
<c:if test="${!empty e}">
    Error: ${e.message}
</c:if>

但是我必须承认我不喜欢 c:catch 方法.它滥用异常来控制流程.如果可以，最好在 servlet 或 JavaBean 中完成这项工作，而不是在 <代码>File#exists()(和ServletContext#getRealPath()).

I must however admit that I don't like the c:catch approach. It's abusing exceptions to control the flow. If you can, rather do this job in a servlet or JavaBean instead with help of File#exists() (and ServletContext#getRealPath()).

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