如何从 Java 过滤器获取请求 URL？

How can I get the request URL from a Java Filter?

提问by ampersandre

I am trying to write a filter that can retrieve the request URL, but I'm not sure how to do so.

我正在尝试编写一个可以检索请求 URL 的过滤器，但我不知道该怎么做。

Here is what I have so far:

这是我到目前为止所拥有的：

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;

public class MyFilter implements Filter {
    public void init(FilterConfig config) throws ServletException { }

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException {
        chain.doFilter(request, response);

        String url = ((HttpServletRequest) request).getPathTranslated();
        System.out.println("Url: " + url);
    }

    public void destroy() { }
}

When I hit a page on my server, the only output I see is "Url: null".

当我点击服务器上的一个页面时，我看到的唯一输出是“Url: null”。

What is the correct way to get the requested URL from a given ServletRequest object in a Filter?

从过滤器中的给定 ServletRequest 对象获取请求的 URL 的正确方法是什么？

采纳答案by Buhake Sindi

Is this what you're looking for?

这是你要找的吗？

if (request instanceof HttpServletRequest) {
 String url = ((HttpServletRequest)request).getRequestURL().toString();
 String queryString = ((HttpServletRequest)request).getQueryString();
}

To Reconstruct:

重建：

System.out.println(url + "?" + queryString);

Info on HttpServletRequest.getRequestURL()and HttpServletRequest.getQueryString().

HttpServletRequest.getRequestURL()和 的信息HttpServletRequest.getQueryString()。

回答by Jigar Joshi

request.getRequestURL();   

• Documentation

• 文档

回答by Brad Parks

Building on another answer on this page,

基于此页面上的另一个答案，

public static String getCurrentUrlFromRequest(ServletRequest request)
{
   if (! (request instanceof HttpServletRequest))
       return null;

   return getCurrentUrlFromRequest((HttpServletRequest)request);
}

public static String getCurrentUrlFromRequest(HttpServletRequest request)
{
    StringBuffer requestURL = request.getRequestURL();
    String queryString = request.getQueryString();

    if (queryString == null)
        return requestURL.toString();

    return requestURL.append('?').append(queryString).toString();
}