while(rs.next())
            {
                i++;
                ub.setUserId(rs.getInt(1));
                ub.setUsername(rs.getString(2));
                ub.setPasswd(rs.getString(3));又是一个典型的错误,你的 ub 所有用的都是一个,应该在循环里初始化
            while(rs.next())
            {
           ub = new UserBean(); // 具体哪个类我就不管了,总之你要new一下
                i++;
                ub.setUserId(rs.getInt(1));
                ub.setUsername(rs.getString(2));
                ub.setPasswd(rs.getString(3));