在转发到JSP时，如何检测Java Servlet中的URL？

问题描述

我有一个看起来像这样的servlet：

I have a servlet that looks something like this:

public class ExampleServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.getWriter().println(request.getPathInfo());
    }
}

带有web.xml映射，如：

with a web.xml mapping like:

<servlet>
    <servlet-name>example</servlet-name>
    <servlet-class>com.example.ExampleServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>example</servlet-name>
    <url-pattern>/example/*</url-pattern>
</servlet-mapping>

它给了我我期望的......如果我去它打印/ foo。但是，如果我将servlet更改为转发到JSP文件：

and it gives me exactly what I expect... If I go to http://localhost:8080/example/foo it prints "/foo". However, if I change the servlet to forward to a JSP file:

public class ExampleServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // do something here to check the value of request.getPathInfo()
        request.getRequestDispatcher("whatever.jsp").forward(request, response);
    }
}

然后当我检查getPathInfo（）的值时现在报告whatever.jsp而不是foo。

then when I check the value of getPathInfo() it now reports "whatever.jsp" instead of "foo".

1. 为什么在转发到JSP之前这已经改变了？


2. 如何检测用户正在寻找的网址？

编辑：万一重要，这是在Google App Engine上。不要认为应该这样。

Just in case it matters this is on Google App Engine. Don't think it should though.

推荐答案

这个问题模糊不清（servlet是否会再次呼唤每个前锋？ ），但听起来很像你需要 request.getAttribute（javax.servlet.forward.request_uri）。

The question is vague and ambiguous (is the servlet calling itself on every forward again?), but it much sounds like that you need request.getAttribute("javax.servlet.forward.request_uri").

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