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.java – Full Java follow redirect example, see comments for self-explanatory.
package com.favtuts.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://www.twitter.com/
URL Content...
<!DOCTYPE html><html dir="ltr" lang="en"><meta charset="utf-8" /> ....Do share if you have better way to handle the HTTP redirection 🙂
Download Source Code
$ git clone https://github.com/favtuts/java-core-tutorials-examples
$ cd java-misc/http