I'm using HttpURLConnection
to retrieve an URL just like that:
URL url = new URL(address);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setInstanceFollowRedirects(true);
// ...
I now want to find out if there was a redirect and if it was a permanent (301) or temporary (302) one in order to update the URL in the database in the first case but not in the second one.
Is this possible while still using the redirect handling of HttpURLConnection
and if, how?
The sendRedirect() method of HttpServletResponse interface can be used to redirect response to another resource, it may be servlet, jsp or html file. It accepts relative as well as absolute URL. It works at client side because it uses the url bar of the browser to make another request.
HttpsURLConnection. HttpsURLConnection. HttpsURLConnection extends HttpURLConnection with support for https-specific features. The abstract class URLConnection is the superclass of all classes that represent a communications link between the application and a URL.
setInstanceFollowRedirects(boolean followRedirects) Sets whether HTTP redirects (requests with response code 3xx) should be automatically followed by this HttpURLConnection instance. void. setRequestMethod(String method)
How do you find the real URL behind the redirect? You can do this in Java using the HttpURLConnection class. Like this: String url = "http://bit.ly/23414"; HttpURLConnection con = (HttpURLConnection) new URL(url).
Simply call getUrl()
on URLConnection
instance after calling getInputStream()
:
URLConnection con = new URL(url).openConnection();
System.out.println("Orignal URL: " + con.getURL());
con.connect();
System.out.println("Connected URL: " + con.getURL());
InputStream is = con.getInputStream();
System.out.println("Redirected URL: " + con.getURL());
is.close();
If you need to know whether the redirection happened before actually getting it's contents, here is the sample code:
HttpURLConnection con = (HttpURLConnection) (new URL(url).openConnection());
con.setInstanceFollowRedirects(false);
con.connect();
int responseCode = con.getResponseCode();
System.out.println(responseCode);
String location = con.getHeaderField("Location");
System.out.println(location);
private HttpURLConnection openConnection(String url) throws IOException {
HttpURLConnection connection;
boolean redirected;
do {
connection = (HttpURLConnection) new URL(url).openConnection();
int code = connection.getResponseCode();
redirected = code == HTTP_MOVED_PERM || code == HTTP_MOVED_TEMP || code == HTTP_SEE_OTHER;
if (redirected) {
url = connection.getHeaderField("Location");
connection.disconnect();
}
} while (redirected);
return connection;
}
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With