Source Code : Java HttpURLConnection follow redirect example

Java HttpURLConnection follow redirect example

The HttpURLConnection‘s follow redirect is just an indicator, in fact it won’t help you to do the “real� http redirection, you still need to handle it manually.

URL obj = new URL(url);
HttpURLConnection conn = (HttpURLConnection) obj.openConnection();
conn.setInstanceFollowRedirects(true);  //you still need to handle redirect manully.
HttpURLConnection.setFollowRedirects(true);1. Java Http Redirect Example
If a server is redirected from the original URL to another URL, the response code should be 301: Moved Permanently or 302: Temporary Redirect. And you can get the new redirected url by reading the “Location� header of the HTTP response header.

For example, access to the normal HTTP twitter website – http://www.twitter.com , it will auto redirect to the HTTPS twitter website – https://www.twitter.com.

HttpRedirectExample – Full Java follow redirect example, see comments for self-explanatory.
package com.mkyong.http;
 
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
 
public class HttpRedirectExample {
 
  public static void main(String[] args) {
 
  try {
 
   String url = "http://www.twitter.com";
 
   URL obj = new URL(url);
   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");
 
   System.out.println("Request 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;
   }
 
   System.out.println("Response Code ... " + status);
 
   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 = (HttpURLConnection) new URL(newUrl).openConnection();
     conn.setRequestProperty("Cookie", cookies);
     conn.addRequestProperty("Accept-Language", "en-US,en;q=0.8");
     conn.addRequestProperty("User-Agent", "Mozilla");
     conn.addRequestProperty("Referer", "google.com");
 
     System.out.println("Redirect to URL : " + newUrl);
 
   }
 
   BufferedReader in = new BufferedReader(
  new InputStreamReader(conn.getInputStream()));
   String inputLine;
   StringBuffer html = new StringBuffer();
 
   while ((inputLine = in.readLine()) != null) {
     html.append(inputLine);
   }
   in.close();
 
   System.out.println("URL Content... \n" + html.toString());
   System.out.println("Done");
 
  } catch (Exception e) {
   e.printStackTrace();
  }
 
  }
 
}

Output

Request URL ... http://www.twitter.com
Response Code ... 301
Redirect to URL : https://twitter.com/
URL Content...