code: public User get(Connection conn,String loginname, String cryptpassword) throws SQLException {
          ResultSetHandler<User> h = new BeanHandler<User>(User.class);
          String sql =
              "SELECT id,username,fullname,type,emailaddress,registered_ts,invited_by,enabled \n"+
              "FROM userbase \n";
          if (loginname.indexOf("@") < 0)
              sql = sql + "WHERE username=? AND password=? and enabled=true";
          else
              sql = sql + "WHERE emailaddress=? AND password=? and enabled=true";
          return run.query(conn, sql, h, loginname, cryptpassword);
      }
docs: {@inheritDoc}
  <p>
  安全考虑，返回 User 的 password 属性为 null。</p>