Getting access token for Google adwords

Question

I am using the following code to get acces token from Google Adwords but it is showing error 400 with

grant_type:invalid code:invalid

Though my auth code should be correct. Can anybody tell me what am I missing here?

public void AccessToken()  
{  
    //Getting access token from google 
    redirect_uri = encodingutil.urlEncode(redirect_uri, 'UTF-8'); 
    code = encodingutil.urlEncode(code , 'UTF-8'); 
    secret  = encodingutil.urlEncode(secret , 'UTF-8'); 
    key = encodingutil.urlEncode(key, 'UTF-8'); 

    HttpRequest req = new HttpRequest();  
    req.setMethod('POST');  
    req.setEndpoint('https://accounts.google.com/o/oauth2/token');  
    req.setHeader('content-type', 'application/x-www-form-urlencoded');  
    String messageBody = 'code='+code+'&client_id='+key+'&client_secret='+secret+'&redirect_uri='+redirect_uri+'&grant_type=authorization_code';  
    req.setHeader('Content-length', String.valueOf(messageBody.length()));  
    req.setBody(messageBody);  
    req.setTimeout(60*1000);  

    Http h = new Http();  
    String resp;  
    HttpResponse res = h.send(req);  
    resp = res.getBody();  

    System.debug(' jsonresponse ' + resp);  
   }
}

Is this rest service is applicable for Google adwords?

Answer 1

Try with this:

    HttpRequest req = new HttpRequest();  
    req.setMethod('POST');  
    req.setEndpoint('https://accounts.google.com/o/oauth2/token?code='+code+'&client_id='+key+'&client_secret='+secret+'&redirect_uri='+redirect_uri+'&grant_type=authorization_code'');  
    req.setHeader('content-type', 'application/x-www-form-urlencoded');   
    req.setHeader('Content-length', String.valueOf(messageBody.length()));    
    req.setTimeout(60*1000);  

You need to set parameter in endpoint not in request body.