返回说明:
a) 正确时返回的JSON数据包如下:
{"access_token":"ACCESS_TOKEN","expires_in":7200,"scope":"SCOPE","refresh_token":"REFRESH_TOKEN","openid":"OPENID"}
b)错误时返回的JSON数据包如下:
{"error":"invalid_grant","error_description":"Authorizationcode doesn't exist or is invalid for the client"}