https://qooah.com/2014/11/18/google-wallet-api-%e6%98%8e%e5%b9%b4%e5%b0%87%e7%84%a1%e6%b3%95%e8%b3%bc%e8%b2%b7%e8%99%9b%e6%93%ac%e7%89%a9%e5%93%81/