iOS HTTP Post Redirection Handler Not Working

Question

I am new to iOS development. I was just trying to do a post request to a server, but encountered problems mentioned here with server redirection. I used the event handler mentioned in the answer, but things still do not work right.

Here is my .m code:

@interface ViewController ()

@end

@implementation ViewController


#pragma mark NSURLConnection Delegate Methods


//CALL BACK METHODS

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
    NSLog(@"    didReceiveResponse");
    // A response has been received, this is where we initialize the instance var you created
    // so that we can append data to it in the didReceiveData method
    // Furthermore, this method is called each time there is a redirect so reinitializing it
    // also serves to clear it


    //initialize response
    _responseData = [[NSMutableData alloc] init];

}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
    NSLog(@"   didReceiveData");
    // Append the new data to the instance variable you declared
    [_responseData appendData:data];



}

- (NSCachedURLResponse *)connection:(NSURLConnection *)connection
                  willCacheResponse:(NSCachedURLResponse*)cachedResponse {
    // Return nil to indicate not necessary to store a cached response for this connection
    return nil;
}




- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
    NSLog(@"   connectionDidFinishLoading ");

    // The request is complete and data has been received
    // You can parse the stuff in your instance variable now

    NSString *dataReceived= [[NSString alloc] initWithData:_responseData encoding:NSUTF8StringEncoding];
    NSLog(@"    async response data: %@", dataReceived);



}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
    NSLog(@"   didFailWithError");

    // The request has failed for some reason!
    // Check the error var
}



- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.


    NSString *post = [NSString stringWithFormat:@"&j_username=%@&j_password=%@",@"usrname",@"pw"];
    NSData *postData = [post dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];

    NSString *postLength = [NSString stringWithFormat:@"%d", [postData length]];

    request = [[NSMutableURLRequest alloc] init];
    request.HTTPMethod= @"POST";
    //parameters
    [request setURL:[NSURL URLWithString:@"url"]];
    [request setValue:postLength forHTTPHeaderField:@"Content-Length"];
    [request setValue:@"application/x-www-form-urlencoded;charset=UTF-8" forHTTPHeaderField:@"Content-Type"];
    [request setValue:@"XMLHttpRequest" forHTTPHeaderField:@"X-Requested-With"];
    [request setHTTPBody:postData];




    // Send a synchronous request
    if (0) {
        NSURLResponse * response = nil;
        NSError * error = nil;
        NSData * data = [NSURLConnection sendSynchronousRequest:request
                                              returningResponse:&response
                                                          error:&error];
        NSLog(@"  Synchronous request done");
        if (error == nil)
        {
            // Parse data here
            NSLog(@"     Synchronous response has no error");
            NSLog(@"    Synchronous Reply: %@", response);
        }
    }
    else {
        // Send Asynchronous request
        //NSURLConnection *conn = [[NSURLConnection alloc] initWithRequest:request delegate:self];
        [NSURLConnection connectionWithRequest:request delegate:self];
        NSLog(@"  Asynchronous request sent");
    }



}

- (NSURLRequest *)connection: (NSURLConnection *)connection
             willSendRequest: (NSURLRequest *)inRequest
            redirectResponse: (NSURLResponse *)redirectResponse;
{
    if (redirectResponse) {
        // we don't use the new request built for us, except for the URL
        NSURL *newURL = [request URL];
        NSString *redirectURL= [newURL absoluteString];
        NSLog(@"Redirect URL: ");
        NSLog(redirectURL);
        // Previously, store the original request in _originalRequest.
        // We rely on that here!
        NSMutableURLRequest *newRequest = [request mutableCopy];
        [newRequest setURL: newURL];
        NSLog(@"redirect occur");
        return newRequest;
    } else {
        NSLog(@"no redirect");
        return inRequest;
    }
}

@end

Without the handler, the request goes through fine(just without the body attached); but with the handler, the redirection gets detected again and again b/c the redirected url is same as the original. Eventually the requested died because of too many redirects. I think this might be a server end problem, but am I doing anything wrong in the coding that causes this?

Answer 1

Basically the problem was that the url of the redirectResponse wasn't where you were redirected to; it's still the same one you set in the original post method. That was why you were being redirected to the same url again and again.

So what you wanna do is intercepting the actual url you are being redirected to in the response headers. After your initial post request was executed, you should get response headers like this:

HTTP/1.1 302 Found
Location: http://www.iana.org/domains/example/

where "Location" indicates where you are being redirected to. So get the url like so:

NSDictionary* headers = [(NSHTTPURLResponse *)redirectResponse allHeaderFields];
NSString newUrl=headers[@"Location"];

Use newUrl in your newRequest, then you should be good to go.