(MFC) REST Follow Redirects

Demonstrates how to follow a 302/303 redirect response.

Chilkat C/C++ Library Downloads MS Visual C/C++ Libs

See Also: Using MFC CString in Chilkat

#include <CkRest.h>
#include <CkUrl.h>

void ChilkatSample(void)
    {
    CkString strOut;

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkRest rest;

    bool bTls = true;
    int port = 443;
    bool bAutoReconnect = true;
    bool success = rest.Connect("chilkatsoft.com",port,bTls,bAutoReconnect);
    if (success != true) {
        strOut.append(rest.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Send a POST to a URL that will respond with a 302 redirect..
    rest.AddQueryParam("firstName","John");
    rest.AddQueryParam("lastName","Doe");
    const char *responseText = rest.fullRequestFormUrlEncoded("POST","/echoPost302.asp");
    if (rest.get_LastMethodSuccess() != true) {
        strOut.append(rest.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    int statusCode = rest.get_ResponseStatusCode();

    // Examine the response status code
    if (statusCode < 300) {
        strOut.append("Not a redirect.");
        strOut.append("\r\n");
        strOut.append(responseText);
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    if (statusCode > 399) {
        strOut.append("Error response: Status code = ");
        strOut.appendInt(statusCode);
        strOut.append("\r\n");
        strOut.append(responseText);
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    strOut.append("Redirect status code = ");
    strOut.appendInt(statusCode);
    strOut.append("\r\n");

    // 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.

    strOut.append(rest.responseHeader());
    strOut.append("\r\n");

    CkUrl *redirectUrl = rest.RedirectUrl();
    if (rest.get_LastMethodSuccess() == false) {
        strOut.append("No Location header found for redirect.");
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        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) {
        strOut.append(rest.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        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) {
            strOut.append(rest.lastErrorText());
            strOut.append("\r\n");
            SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
            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) {
            strOut.append(rest.lastErrorText());
            strOut.append("\r\n");
            SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
            return;
        }

    }

    // Show the final status code and the response text.
    strOut.append("Final status code = ");
    strOut.appendInt(rest.get_ResponseStatusCode());
    strOut.append("\r\n");

    strOut.append("Final response text (HTML, XML, JSON, or whatever..)");
    strOut.append("\r\n");
    strOut.append(responseText);
    strOut.append("\r\n");


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }