mysql如何向mongodb转化

/**
* 校验用户名是否注册
* @param loginname
* @return
* @throws SQLException
*/
public boolean ajaxValidateLoginname(String loginname) throws SQLException {
String sql = "select count(1) from t_user where loginname=?";
Number number = (Number)qr.query(sql, new ScalarHandler(), loginname);
return number.intValue() == 0;
}

/** * 校验Email是否注册 * @param email * @return * @throws SQLException */public boolean ajaxValidateEmail(String email) throws SQLException {    String sql = "select count(1) from t_user where email=?";    Number number = (Number)qr.query(sql, new ScalarHandler(), email);    return number.intValue() == 0;}/** * 用户名注册校验 * @param loginname * @return */public boolean ajaxValidateLoginname(String loginname) {    try {        return userDao.ajaxValidateLoginname(loginname);    } catch (SQLException e) {        throw new RuntimeException(e);    }}/** * Email校验 * @param email * @return */public boolean ajaxValidateEmail(String email) {    try {        return userDao.ajaxValidateEmail(email);    } catch (SQLException e) {        throw new RuntimeException(e);    }}这是用mysql语法写的，如果用的是mongo该怎么写呢，求教