(Java) REST Follow Redirects

Demonstrates how to follow a 302/303 redirect response.

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import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkRest rest = new CkRest();

    boolean bTls = true;
    int port = 443;
    boolean bAutoReconnect = true;
    boolean success = rest.Connect("chilkatsoft.com",port,bTls,bAutoReconnect);
    if (success != true) {
        System.out.println(rest.lastErrorText());
        return;
        }

    // Send a POST to a URL that will respond with a 302 redirect..
    rest.AddQueryParam("firstName","John");
    rest.AddQueryParam("lastName","Doe");
    String responseText = rest.fullRequestFormUrlEncoded("POST","/echoPost302.asp");
    if (rest.get_LastMethodSuccess() != true) {
        System.out.println(rest.lastErrorText());
        return;
        }

    int statusCode = rest.get_ResponseStatusCode();

    // Examine the response status code
    if (statusCode < 300) {
        System.out.println("Not a redirect.");
        System.out.println(responseText);
        return;
        }

    if (statusCode > 399) {
        System.out.println("Error response: Status code = " + statusCode);
        System.out.println(responseText);
        return;
        }

    System.out.println("Redirect status code = " + statusCode);

    // The response header will contain a Location field with the redirect URL, such as this:
    // Location: http://www.chilkatsoft.com/echoPostFinal.asp

    // The response status code determines how the client should behave.
    // Here are some common possibilities:

    // 301: Moved Permanently
    // This and all future requests should be directed to the given URI.  (Keep the original HTTP method for the redirect.  In this case, the 
    // original request was a POST, so we POST to the redirect URL.)

    // 302: Found (aka Object Moved aka Moved Temporarily)
    // This is the most popular redirect code, but also an example of industrial practice contradicting the standard. HTTP/1.0 specification (RFC 1945 ) required the client
    // to perform a temporary redirect (the original describing phrase was Moved Temporarily), but popular browsers implemented it as a 303 See Other. Therefore, HTTP/1.1
    // added status codes 303 and 307 to disambiguate between the two behaviors. However, the majority of Web applications and frameworks still use the 302 status code
    // as if it were the 303.

    // 303: See Other
    // The response to the request can be found under another URI using a GET method. When received in response to a PUT, it should be assumed that the server has
    // received the data and the redirect should be issued with a separate GET message.

    // 307: Temporary Redirect
    // In this occasion, the request should be repeated with another URI, but future requests can still use the original URI. In contrast to 303, the request method
    // should not be changed when reissuing the original request. For instance, a POST request must be repeated using another POST request.

    System.out.println(rest.responseHeader());

    CkUrl redirectUrl = rest.RedirectUrl();
    if (rest.get_LastMethodSuccess() == false) {
        System.out.println("No Location header found for redirect.");
        return;
        }

    // Prep for the redirect..
    rest.ClearAllParts();

    // Disconnect and re-connect.  
    // (This can be skipped if both the host and SSL/TLS conditions are the same.)
    rest.Disconnect(100);
    success = rest.Connect(redirectUrl.host(),redirectUrl.get_Port(),redirectUrl.get_Ssl(),bAutoReconnect);
    if (success != true) {
        System.out.println(rest.lastErrorText());
        return;
        }

    if ((statusCode == 301) || (statusCode == 307)) {
        // Redirect using a POST, sending the same params to the new destination
        rest.AddQueryParam("firstName","John");
        rest.AddQueryParam("lastName","Doe");
        responseText = rest.fullRequestFormUrlEncoded("POST",redirectUrl.path());
        if (rest.get_LastMethodSuccess() != true) {
            System.out.println(rest.lastErrorText());
            return;
            }

        }

    if ((statusCode == 302) || (statusCode == 303)) {
        // Redirect using a GET, sending the query params found in the redirect URL.
        responseText = rest.fullRequestFormUrlEncoded("GET",redirectUrl.pathWithQueryParams());
        if (rest.get_LastMethodSuccess() != true) {
            System.out.println(rest.lastErrorText());
            return;
            }

        }

    // Show the final status code and the response text.
    System.out.println("Final status code = " + rest.get_ResponseStatusCode());

    System.out.println("Final response text (HTML, XML, JSON, or whatever..)");
    System.out.println(responseText);
  }
}