Java - 如何查找网址的重定向网址？ [英] Java - How to find the redirected url of a url?

问题描述

我通过java访问网页如下：

I am accessing web pages through java as follows:

URLConnection con = url.openConnection();

但在某些情况下，网址会重定向到另一个网址。所以我想知道上一个网址重定向的网址。

But in some cases, a url redirects to another url. So I want to know the url to which the previous url redirected.

以下是我收到的标题字段：

Below are the header fields that I got as a response:

null-->[HTTP/1.1 200 OK]
Cache-control-->[public,max-age=3600]
last-modified-->[Sat, 17 Apr 2010 13:45:35 GMT]
Transfer-Encoding-->[chunked]
Date-->[Sat, 17 Apr 2010 13:45:35 GMT]
Vary-->[Accept-Encoding]
Expires-->[Sat, 17 Apr 2010 14:45:35 GMT]
Set-Cookie-->[cl_def_hp=copenhagen; domain=.craigslist.org; path=/; expires=Sun, 17     Apr 2011 13:45:35 GMT, cl_def_lang=en; domain=.craigslist.org; path=/; expires=Sun, 17 Apr 2011 13:45:35 GMT]
Connection-->[close]
Content-Type-->[text/html; charset=iso-8859-1;]
Server-->[Apache]

所以目前，我正在从 Set-Cookie 标题字段的值构建重定向的url。在上面的例子中，重定向的网址是 copenhagen.craigslist.org

So at present, I am constructing the redirected url from the value of the Set-Cookie header field. In the above case, the redirected url is copenhagen.craigslist.org

我有什么标准方式可以通过可以确定特定网址要重定向的网址。

Is there any standard way through which I can determine which url the particular url is going to redirect.

我知道当网址重定向到其他网址时，服务器会发送包含<$ c $的中间响应c>位置标题字段，告诉重定向的URL，但我没有通过 url.openConnection（）; 方法接收该中间响应。

I know that when a url redirects to other url, the server sends an intermediate response containing a Location header field that tells the redirected url but I am not receiving that intermediate response through the url.openConnection(); method.

推荐答案

您需要将 URLConnection 转换为 HttpURLConnection 并通过设置不关注重定向/net/HttpURLConnection.html#setInstanceFollowRedirects%28boolean%29\"rel =noreferrer> HttpURLConnection＃setInstanceFollowRedirects（） 到 false 。您也可以通过全局设置它 HttpURLConnection＃setFollowRedirects（） 。

You need to cast the URLConnection to HttpURLConnection and instruct it to not follow the redirects by setting HttpURLConnection#setInstanceFollowRedirects() to false. You can also set it globally by HttpURLConnection#setFollowRedirects().

您只需要自己处理重定向。通过 <$查看回复代码c $ c> HttpURLConnection＃getResponseCode（） ，通过位置标题。 sun.com/javase/6/docs/api/java/net/URLConnection.html#getHeaderField%28java.lang.String%29rel =noreferrer> URLConnection＃getHeaderField（） 然后在其上发出新的HTTP请求。

You only need to handle redirects yourself then. Check the response code by HttpURLConnection#getResponseCode(), grab the Location header by URLConnection#getHeaderField() and then fire a new HTTP request on it.

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