使用进行返回附加的 servlet 调用，但它们没有被呈现

发布于 2024-12-06 01:49:29 字数 1422 浏览 1 评论 0原文

所以这个问题建议在执行包含之前使用 servlet 进行文件检查：如何检查在 JSP 中包含/导入文件之前是否存在该文件？

所以我编写了一个 servlet 来执行此操作。我使用类似的方式来调用它，

<jsp:include page='<%= "/servlet/fileChecker?section=THX&file=1138" &>'></jsp:include>

但是该 servlet 调用的输出包含一个 jsp:include 标记，指向我正在检查的文件。不幸的是，浏览器不“包含”它。我收到诸如“没有属性‘page’”和“元素‘jsp:include’未定义”之类的错误——这表明 servlet 输出没有呈现为 Java，而是呈现为 HTML。

这是输出：

<p>Text before the servlet call</p>
    <p><h4>From THX1138</h4><jsp:include page='thx/results_1138.jsp'></jsp:include></p>
<p>Text after the servlet call</p>

这是我的 servlet 的主要调用：

private String FileChecker(String section, String file) {
    String result = ""; // assume file does not exist

    String pathToCheck = section + "/results_" + file + ".jsp";
    // realPath is defined in the init() method as config.getServletContext().getRealPath("/");
    File fileToCheck = new File(realPath + pathToCheck);
    if (fileToCheck.exists()) {
        result = "<p><h4>" + section + "</h4><jsp:include page='" + pathToCheck + "'></jsp:include></p>";
    }

    return result;
}

我觉得答案很接近，但我不确定我应该在后面看什么窗帘。有什么帮助吗？

原文

So this question suggested using a servlet to do the file check before doing the include:
How can you check if a file exists before including/importing it in JSP?

So I wrote a servlet that does that. I call it using something like

<jsp:include page='<%= "/servlet/fileChecker?section=THX&file=1138" &>'></jsp:include>

but the output of that servlet call contains a jsp:include tag, to the file I was checking for. Unfortunately, the browser doesn't "include" it. I'm getting errors like "there is no attribute 'page'" and "element 'jsp:include' undefined" -- which suggests the servlet output is not being rendered as Java but as HTML.

Here is the output:

<p>Text before the servlet call</p>
    <p><h4>From THX1138</h4><jsp:include page='thx/results_1138.jsp'></jsp:include></p>
<p>Text after the servlet call</p>

Here is the main call of my servlet:

private String FileChecker(String section, String file) {
    String result = ""; // assume file does not exist

    String pathToCheck = section + "/results_" + file + ".jsp";
    // realPath is defined in the init() method as config.getServletContext().getRealPath("/");
    File fileToCheck = new File(realPath + pathToCheck);
    if (fileToCheck.exists()) {
        result = "<p><h4>" + section + "</h4><jsp:include page='" + pathToCheck + "'></jsp:include></p>";
    }

    return result;
}

I feel like the answer is close, but I'm not sure what curtain I should be looking behind. Any help?

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入画浅相思 2024-12-13 01:49:29

不要将带有一堆 HTML 和 JSP 标记的字符串写入响应。这毫无意义。 Web 浏览器不理解 JSP 标签。

请改为调用 RequestDispatcher#include()。

request.getRequestDispatcher(checkedJspPath).include(request, response);

并将该 HTML 移回到 JSP 中。

与具体问题无关，我知道您指的是我的旧答案，但我意识到实际上最好检查 ServletContext#getResource() 是否不存在不返回 null，而是使用 File#exists()。这样，只要 WAR 不扩展，它就可以正常工作。

Do not write a string with a bunch of HTML and JSP tags to the response. This makes no sense. The webbrowser does not understand JSP tags.

Call RequestDispatcher#include() instead.

request.getRequestDispatcher(checkedJspPath).include(request, response);

And move that HTML back into the JSP.

Unrelated to the concrete question, I know that you're referring to an old answer of me, but I realize that it's actually better to check if ServletContext#getResource() doesn't return null instead of using File#exists(). This way it'll work as well whenever the WAR is not expanded.

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