java サーブレットと postgresql の接続に問題があります。できれば助けてください
String dbName = "jdbc:postgresql://localhost/schedule_of_holidays";
String dbDriver = "org.postgresql.Driver";
Class.forName(dbDriver);
Connection con = DriverManager.getConnection(dbName, userName,
password);
System.out.println("Got Connection");
Statement statement = con.createStatement();
String sql = "select id from registration";
ResultSet rs = statement.executeQuery(sql);
while (rs.next()) {
System.out.println(rs.getInt("id"));
}