//base64 encode
public static String encode(String s) {
        if (s == null)
            return null;
        String res = "";
        try {
            res = new sun.misc.BASE64Encoder().encode(s.getBytes("GBK"));
        } catch (UnsupportedEncodingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return res;
}

//base64 decode
public static String decode(String s) {
        if (s == null)
            return null;
        BASE64Decoder decoder = new BASE64Decoder();
        try {
            byte[] b = decoder.decodeBuffer(s);
            return new String(b,"GBK");
        } catch (Exception e) {
            return null;
        }
}