url - Getting "java.net.ProtocolException: Server redirected too many times" Error

Question

I'm making a simple URL request with code like this:

URL url = new URL(webpage);
URLConnection urlConnection = url.openConnection();
InputStream is = urlConnection.getInputStream();

But on that last line, I'm getting the "redirected too many times error". If my "webpage" var is, say, google.com then it works fine, but when I try to use my servlet's URL then it fails. It seems I can adjust the number of times it follows the redirects (default is 20) with this:

System.setProperty("http.maxRedirects", "100");

But when I crank it up to, say, 100 it definitely takes longer to throw the error so I know it is trying. However, the URL to my servlet works fine in (any) browser and using the "persist" option in firebug it seems to only be redirecting once.

A bit more info on my servlet ... it is running in tomcat and fronted by apache using 'mod-proxy-ajp'. Also of note, it is using form authentication so any URL you enter should redirect you to the login page. As I said, this works correctly in all browsers, but for some reason the redirect isn't working with the URLConnection in Java 6.

Thanks for reading ... ideas?

Answer 1

It's apparently redirecting in an infinite loop because you don't maintain the user session. The session is usually backed by a cookie. You need to create a CookieManager before you use URLConnection.

// First set the default cookie manager.
CookieHandler.setDefault(new CookieManager(null, CookiePolicy.ACCEPT_ALL));

// All the following subsequent URLConnections will use the same cookie manager.
URLConnection connection = new URL(url).openConnection();
// ...

connection = new URL(url).openConnection();
// ...

connection = new URL(url).openConnection();
// ...

See also:

• Using java.net.URLConnection to fire and handle HTTP requests