How auto redirect in HttpClient (java, apache)

Question

I create httpClient and set settings

HttpClient client = new HttpClient();

client.getParams().setCookiePolicy(CookiePolicy.BROWSER_COMPATIBILITY);
client.getParams().setContentCharset("UTF-8");

First request (get)

GetMethod first = new GetMethod("http://vk.com");
int returnCode = client.executeMethod(first);

BufferedReader br = null;
String lineResult = "";
if (returnCode == HttpStatus.SC_NOT_IMPLEMENTED) {
    System.err.println("The Post method is not implemented by this URI");
    // still consume the response body
    first.getResponseBodyAsString();
} else {
    br = new BufferedReader(new InputStreamReader(first.getResponseBodyAsStream(), Charset.forName("windows-1251")));
    String readLine = "";
    while (((readLine = br.readLine()) != null)) {
        lineResult += readLine;
    }
}

Response correct.

Second request (post):

PostMethod second = new PostMethod("http://login.vk.com/?act=login");

second.setRequestHeader("Referer", "http://vk.com/");

second.addParameter("act", "login");
second.addParameter("al_frame", "1");
second.addParameter("captcha_key", "");
second.addParameter("captcha_sid", "");
second.addParameter("expire", "");
second.addParameter("q", "1");
second.addParameter("from_host", "vk.com");
second.addParameter("email", email);
second.addParameter("pass", password);

returnCode = client.executeMethod(second);

br = null;
lineResult = "";
if (returnCode == HttpStatus.SC_NOT_IMPLEMENTED) {
    System.err.println("The Post method is not implemented by this URI");
    // still consume the response body
    second.getResponseBodyAsString();
} else {
    br = new BufferedReader(new InputStreamReader(second.getResponseBodyAsStream()));
    String readLine = "";
    while (((readLine = br.readLine()) != null)) {
        lineResult += readLine;
    }
}

this response is correct too, but I need to be redirected to Headers.Location.

I do not know how to get value from Headers Location or how to automatically enable redirection.

Solution 1

Due to design limitations HttpClient 3.x is unable to automatically handle redirects of entity enclosing requests such as POST and PUT. You either have to manually convert POST request to a GET upon redirect or upgrade to HttpClient 4.x, which can handle all types of redirects automatically.

Solution 2

In case of the 3.x version of HttpClient, you can also check if the response code is 301 or 302 and then use the Location header to re-post:

client.executeMethod(post);
int status = post.getStatusCode();
if (status == 301 || status == 302) {
  String location = post.getResponseHeader("Location").toString();
  URI uri = new URI(location, false);
  post.setURI(uri);
  client.executeMethod(post);
}

Comments

[Mediator]

Error - "Entity enclosing requests cannot be redirected without user intervention"

[Dilini]

You might have to use post.getResponseHeader("Location").getValue();