Parsing Facebook signed using java_ Request will return malformed JSON

I'm trying to parse Facebook signed in dopost of java servlet_ request. I use Base64 of Commons - codec - 1.3 to decode signed requests

String signedRequest = (String) req.getParameter("signed_request");
String payload = signedRequest.split("[.]",2)[1];
payload = payload.replace("-","+").replace("_","/").trim();
String jsonString = new String(Base64.decodeBase64(payload.getBytes()));

When I system Out jsonstring its format is incorrect Sometimes it misses the end of JSON} sometimes it misses "} at the end of the string

How do I get the correct JSON response from Facebook?

Solution

Facebook is using Base64 for URL. You may be trying to decode text using standard Base64 algorithm

>You can add the required characters (padding, etc.) > you can use commons codec 1.5 (New Base64 (true)), where they add support for this coding