使用 url 模式“/*"的 servlet 映射中的 StackOverflowError [英] StackOverflowError in servlet mapping with url-pattern "/*"

问题描述

我有一组 JSP 页面，我想隐藏 .jsp 扩展名(经过一些研究，它似乎对 SEO 有好处).

I have a set of JSP pages and I want to hide the .jsp extension (after a bit of research it seems it's good for SEO).

我遇到的一个解决方案如下:

One solution I came across was the following:

<servlet>
    <servlet-name>mypage</servlet-name>
    <jsp-file>/some-page.jsp</jsp-file>
</servlet>
<servlet-mapping>
    <servlet-name>mypage</servlet-name>
    <url-pattern>/some-page</url-pattern>
</servlet-mapping>

虽然这有效，但我相信我必须为我网站上的每个 jsp 页面设置此映射.

And while this works, I believe I have to set up this mapping for every jsp page on my site.

我在这里发布了另一个解决方案(简单友好的 URL):隐藏功能JSP/Servlet

I came across another solution posted here (Easy friendly URL's): Hidden features of JSP/Servlet

... 它使用一个简单的 servlet 来转发请求.在我的 web.xml 中，我有以下内容并且工作正常:

... which uses a simple servlet to forward the request. In my web.xml I have the following and it works fine:

<servlet>
    <servlet-name>MyServletName</servlet-name>
    <servlet-class>myservlets.PrettyUrlServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>MyServletName</servlet-name>
    <url-pattern>/myservlet/*</url-pattern>
</servlet-mapping>

现在的问题是我不想点击 URL:www.mydomain.com/myservlet/some-page

Now the problem is I don't want to hit the URL: www.mydomain.com/myservlet/some-page

我想使用网址:www.mydomain.com/some-page

I want to use the URL: www.mydomain.com/some-page

所以我将 url-pattern 更改为/*"

So I changed the url-pattern to "/*"

<servlet>
    <servlet-name>MyServletName</servlet-name>
    <servlet-class>myservlets.PrettyUrlServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>MyServletName</servlet-name>
    <url-pattern>/*</url-pattern>
</servlet-mapping>

但这会导致无限循环:

    Exception in thread "http-bio-8080-exec-1" java.lang.StackOverflowError
            at org.apache.catalina.core.ApplicationHttpRequest.getAttribute(ApplicationHttpRequest.java:219)
            at org.apache.catalina.core.ApplicationHttpRequest.getAttribute(ApplicationHttpRequest.java:228)
            .
            .
            at org.apache.catalina.core.ApplicationHttpRequest.getAttribute(ApplicationHttpRequest.java:228)
            at org.apache.catalina.core.ApplicationHttpRequest.getAttribute(ApplicationHttpRequest.java:228)
            at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:379)
            at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:329)
            at myservlets.PrettyUrlServlet.doGet(PrettyUrlServlet.java:22)

我不知道如何解决.有什么想法吗?

Which I'm not sure how to fix. Any ideas?

推荐答案

映射在 /* 上的 servlet 也将在 RequestDispatcher#forward() 调用上运行.因此，如果您在该 servlet 中执行转发，它每次都会在无限循环中调用自己.这解释了 StackOverflowError.

A servlet which is mapped on /* will also run on RequestDispatcher#forward() calls. So if you're performing a forward in that servlet, it would call itself everytime in an infinite loop. That explains the StackOverflowError.

毕竟，您根本不应该将 /* 用于 servlet.它只对 servlet 过滤器有意义.将 servlet 映射放回更具体的 URL 模式，并在 /* 上创建过滤器，以便在必要时转发到所需的 servlet.您当然不想让 servlet 来处理例如图像/CSS/JS 文件.假设它们都放在 /resources 文件夹中，并且您的前端控制器映射在 /myservlet/* 上，然后在 doFilter() 中执行以下工作:

After all, you should not be using /* for servlets at all. It only makes sense on servlet filters. Put the servlet mapping back on a more specific URL pattern and create a filter on /* which forwards to the desired servlet when necessary. You of course don't want to have the servlet to handle for example images/CSS/JS files. Assuming that they're all placed in /resources folder and that your front controller is mapped on /myservlet/*, then do the following job in doFilter():

HttpServletRequest req = (HttpServletRequest) request;
String path = req.getRequestURI().substring(req.getContextPath().length());

if (path.startsWith("/resources/")) {
    // Just let container's default servlet do its job.
    chain.doFilter(request, response);
}
else {
    // Delegate to your front controller.
    request.getRequestDispatcher("/myservlet" + path).forward(request, response);
}

另见:

• Tomcat 中的 URL 映射到 FrontController servlet

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