如何最有效地获取完整的URL地址? [英] How to get the complete URL address most efficiently?
问题描述
我正在使用Java程序从短网址获取扩展的网址.给定Java URLConnection，在这两种方法中，哪种方法更好地获得期望的结果?
I'm using a Java program to get expanded URLs from short URLs. Given a Java URLConnection, among the two approaches, which one is better to get the desired result?
Connection.getHeaderField("Location");
vs
Connection.getURL();
我想他们两个都给出相同的输出.第一种方法没有给我最好的结果，只有7分之1得到解决.第二种方法可以提高效率吗?
I guess both of them give the same output. The first approach did not give me the best results, only 1 out of 7 were resolved. Can the efficiency be increased by the second approach?
我们可以使用其他更好的方法吗?
Can we use any other better approach?
推荐答案
我将使用以下内容:
@Test
public void testLocation() throws Exception {
final String link = "http://bit.ly/4Agih5";
final URL url = new URL(link);
final HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setInstanceFollowRedirects(false);
final String location = urlConnection.getHeaderField("location");
assertEquals("http://stackoverflow.com/", location);
assertEquals(link, urlConnection.getURL().toString());
}
使用setInstanceFollowRedirects(false)时，HttpURLConnection不会跟随重定向，并且仅从bit.ly的重定向页面将不会下载目标页面(在上例中为stackoverflow.com).
With setInstanceFollowRedirects(false) the HttpURLConnection does not follow redirects and the destination page (stackoverflow.com in the above example) will not be downloaded just the redirect page from bit.ly.
一个缺点是，当解析的bit.ly URL指向例如tinyurl.com上的另一个短URL时，您将获得tinyurl.com链接，而不是tinyurl.com重定向到的链接.
One drawback is that when a resolved bit.ly URL points to another short URL for example on tinyurl.com you will get a tinyurl.com link, not what the tinyurl.com redirects to.
修改:
要查看bit.ly的响应，请使用curl:
To see the reponse of bit.ly use curl:
$ curl --dump-header /tmp/headers http://bit.ly/4Agih5
<html>
<head>
<title>bit.ly</title>
</head>
<body>
<a href="http://stackoverflow.com/">moved here</a>
</body>
</html>
如您所见，bit.ly仅发送一个简短的重定向页面.然后检查HTTP标头:
As you can see bit.ly sends only a short redirect page. Then check the HTTP headers:
$ cat /tmp/headers
HTTP/1.0 301 Moved Permanently
Server: nginx
Date: Wed, 06 Nov 2013 08:48:59 GMT
Content-Type: text/html; charset=utf-8
Cache-Control: private; max-age=90
Location: http://stackoverflow.com/
Mime-Version: 1.0
Content-Length: 117
X-Cache: MISS from cam
X-Cache-Lookup: MISS from cam:3128
Via: 1.1 cam:3128 (squid/2.7.STABLE7)
Connection: close
它发送带有Location标头(指向http://stackoverflow.com/)的301 Moved Permanently响应.现代浏览器不会向您显示上面的HTML页面.相反，它们会自动将您重定向到Location标头中的URL.
It sends a 301 Moved Permanently response with a Location header (which points to http://stackoverflow.com/). Modern browsers don't show you the HTML page above. Instead they automatically redirect you to the URL in the Location header.
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