HttpURLConnection e redirect HTTP

Per decisione degli sviluppatori Java (motivi di sicurezza), l'oggetto HttpURLConnection non segue i redirect HTTP. E' compito di scrive il codice assicurarsi di leggere dall'header HTTP eventuali redirect e seguirli. Il codice seguente mostra come seguire redirect 3xx.

/**
 * Extract the content from an HTTP URL with an HTTP redirect (301, 302, 303)
 * @param url the URL to read 
 * @return the content from an HTTP URL with an HTTP redirect (301, 302, 303)
 */
public String getUrlContentWithRedirect(String url){
	try {
		HttpURLConnection conn = this.openConnection(new URL(url));
		boolean redirect = false;
		// normally, 3xx is redirect
		int status = conn.getResponseCode();
		if (status != HttpURLConnection.HTTP_OK) {
			if (status == HttpURLConnection.HTTP_MOVED_TEMP
				|| status == HttpURLConnection.HTTP_MOVED_PERM
				|| status == HttpURLConnection.HTTP_SEE_OTHER)
				redirect = true;
		}
		if (redirect) {
			// get redirect url from "location" header field
			String newUrl = conn.getHeaderField("Location");
			// get the cookie if need, for login
			String cookies = conn.getHeaderField("Set-Cookie");
			// open the new connnection again
			conn = this.openConnection(new URL(newUrl));
			conn.setRequestProperty("Cookie", cookies);
		}
			
		//read the connection
		return this.getContentFromConnection(conn);
	} catch (Exception e) {
		e.printStackTrace();
	}
	return null;
}
	
/*
 * Open a HttpURLConnection from a URL object
 */
private HttpURLConnection openConnection(URL obj) throws IOException{
	HttpURLConnection conn = (HttpURLConnection) obj.openConnection();
	conn.setReadTimeout(5000);
	conn.addRequestProperty("Accept-Language", "en-US,en;q=0.8");
	conn.addRequestProperty("User-Agent", "Mozilla");
	conn.addRequestProperty("Referer", "google.com");
	return conn;
}