使用Linkedin登录，Oauth2 V2在authorization_code上收到错误

Question

登录成功，我获得了代码和状态。 然后，我正在尝试通过以下链接中的节目中链接的POST请求获取访问令牌：Exchange Authorization Code for an Access Token

这是我的代码（Objective-c）：

-(void)requestForAccessToken:(NSString*)authorizationCode
{
    NSString *grantType = @"authorization_code";

    NSString *redirect = [redirectURL stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet alphanumericCharacterSet]];

    NSString *postParams = [NSString stringWithFormat:@"grant_type=%@&code=%@&redirect_uri=%@&client_id=%@&client_secret=%@", grantType, authorizationCode, redirect, [ELConfig getLinkedinClientId], [ELConfig getLinkedinClientSecret]];

    NSURL *url = [NSURL URLWithString:accessTokenEndPoint];

    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url];
    request.HTTPMethod = @"POST";

    NSData *data = [postParams dataUsingEncoding:NSUTF8StringEncoding];
    request.HTTPBody = data;
    [request addValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];
    NSURLSessionDataTask *task = [[NSURLSession sharedSession]
    dataTaskWithURL:url completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {

        NSError* err;
        NSDictionary* json = [NSJSONSerialization JSONObjectWithData:data
                                                             options:NSJSONReadingMutableContainers
                                                               error:&err];

        NSLog(@"dict: %@", json);
        NSString *accessToken = [json objectForKey:@"access_token"];
        NSLog(@"accessToken: %@", accessToken);
        if (accessToken != nil) {
          [[NSUserDefaults standardUserDefaults] setBool:YES forKey:@"additionalDtaKey"];
          [[NSUserDefaults standardUserDefaults] synchronize];

          dispatch_async(dispatch_get_main_queue(), ^{
            [self popViewController];
          });
        }
    }];
}

[task resume];

-(void)requestForAccessToken:(NSString*)authorizationCode
{
    NSString *grantType = @"authorization_code";

    NSString *redirect = [redirectURL stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet alphanumericCharacterSet]];

    NSString *postParams = [NSString stringWithFormat:@"grant_type=%@&code=%@&redirect_uri=%@&client_id=%@&client_secret=%@", grantType, authorizationCode, redirect, [ELConfig getLinkedinClientId], [ELConfig getLinkedinClientSecret]];

    NSURL *url = [NSURL URLWithString:accessTokenEndPoint];

    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url];
    request.HTTPMethod = @"POST";

    NSData *data = [postParams dataUsingEncoding:NSUTF8StringEncoding];
    request.HTTPBody = data;
    [request addValue:@"application/x-www-form-urlencoded"
        forHTTPHeaderField:@"Content-Type"];
    NSURLSessionDataTask *task = [[NSURLSession sharedSession]
    dataTaskWithURL:url completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {

        NSError* err;
        NSDictionary* json = [NSJSONSerialization JSONObjectWithData:data
                                                             options:NSJSONReadingMutableContainers
                                                               error:&err];

        NSLog(@"dict: %@", json);
        NSString *accessToken = [json objectForKey:@"access_token"];
        NSLog(@"accessToken: %@", accessToken);
        if (accessToken != nil) {
            [[NSUserDefaults standardUserDefaults] setBool:YES forKey:@"additionalDtaKey"];
            [[NSUserDefaults standardUserDefaults] synchronize];

            dispatch_async(dispatch_get_main_queue(), ^{
                [self popViewController];
            });
        }
    }];
    [task resume];
}

和斯威夫特：

func requestForAccessToken(authorizationCode: String) {
    let grantType = "authorization_code"

    let redirectURL = "https://com.test.linkedin.oauth/oauth".stringByAddingPercentEncodingWithAllowedCharacters(NSCharacterSet.alphanumericCharacterSet())!

    // Set the POST parameters.
    var postParams = "grant_type=\(grantType)&"
    postParams += "code=\(authorizationCode)&"
    postParams += "redirect_uri=\(redirectURL)&"
    postParams += "client_id=\(linkedInKey)&"
    postParams += "client_secret=\(linkedInSecret)"

    // Convert the POST parameters into a NSData object.
    let postData = postParams.dataUsingEncoding(NSUTF8StringEncoding)


    // Initialize a mutable URL request object using the access token endpoint URL string.
    let request = NSMutableURLRequest(URL: NSURL(string: accessTokenEndPoint)!)

    // Indicate that we're about to make a POST request.
    request.HTTPMethod = "POST"

    // Set the HTTP body using the postData object created above.
    request.HTTPBody = postData

    // Add the required HTTP header field.
    request.addValue("application/x-www-form-urlencoded;", forHTTPHeaderField: "Content-Type")


    // Initialize a NSURLSession object.
    let session = NSURLSession(configuration: NSURLSessionConfiguration.defaultSessionConfiguration())

    // Make the request.
    let task: NSURLSessionDataTask = session.dataTaskWithRequest(request) { (data, response, error) -> Void in
        // Get the HTTP status code of the request.
        let statusCode = (response as! NSHTTPURLResponse).statusCode

        if statusCode == 200 {
            // Convert the received JSON data into a dictionary.
            do {
                let dataDictionary = try NSJSONSerialization.JSONObjectWithData(data!, options: NSJSONReadingOptions.MutableContainers)

                let accessToken = dataDictionary["access_token"] as! String

                NSUserDefaults.standardUserDefaults().setObject(accessToken, forKey: "LIAccessToken")
                NSUserDefaults.standardUserDefaults().synchronize()

                dispatch_async(dispatch_get_main_queue(), { () -> Void in
                    self.dismissViewControllerAnimated(true, completion: nil)
                })
            }
            catch {
                print("Could not convert JSON data into a dictionary.")
            }
        }
    }
    task.resume()
}

我总是遇到以下错误：

{
    error = "missing_parameter";
    "error_description" = "A required parameter \"client_id\" is missing";
}