SELECT * FROM user WHERE user_id = *

user_id = 全部 怎么写

补充代码，如果为空， urlname = ???; name = ???; email = ???; 这3个怎么写

javapublic User get(String urlname, String name, String email) {
    try {
        if (urlname == null) {
            urlname = ???;
        }
        if (name == null) {
            name = ???;
        }
        if (email == null) {
            email = ???;
        }
        String sql = "SELECT * FROM tz_user WHERE deleting = 0 AND urlname = ? AND name = ? AND email = ?";
        RowMapper<User> rowMapper = new BeanPropertyRowMapper<User>(User.class);
        User user = jdbcTemplate.queryForObject(sql, rowMapper, urlname, name, email);
        return user;
    } catch (Exception e) {
        return null;
    }
}