public static String getSha1(String str){

        if(str==null||str.length()==0){

            return null;

        }

        char hexDigits[] = {'0','1','2','3','4','5','6','7','8','9',

                'a','b','c','d','e','f'};

        try {

            MessageDigest mdTemp = MessageDigest.getInstance("SHA1");

            mdTemp.update(str.getBytes("UTF-8"));

            byte[] md = mdTemp.digest();

            int j = md.length;

            char buf[] = new char[j*2];

            int k = 0;

            for (int i = 0; i < j; i++) {

                byte byte0 = md[i];

                buf[k++] = hexDigits[byte0 >>> 4 & 0xf];

                buf[k++] = hexDigits[byte0 & 0xf];

            }

            return new String(buf);

        } catch (Exception e) {

            // TODO: handle exception

            return null;

        }

    }