This section describes the ResultSet cursor initial position: before first row. next() should be called to move the cursor to the first row.
Right after the ResultSet object is returned from the executeQuery() call,
the ResultSet cursor is positioned before the first row.
You need to call next() once to move the cursor to the first row.
If you missed this call, you will get an error message as shown by this sample program:
/**
* DerbyResultSetNoNext.java
* Copyright (c) 2007 by Dr. Herong Yang. All rights reserved.
*/
import java.sql.*;
public class DerbyResultSetNoNext {
public static void main(String [] args) {
Connection con = null;
try {
con = DriverManager.getConnection(
"jdbc:derby://localhost/TestDB");
Statement sta = con.createStatement();
// Catch the ResultSet object
ResultSet res = sta.executeQuery("SELECT * FROM Profile");
// Skip calling next()
// res.next();
// Try to get column values
String firstName = res.getString("FirstName");
String lastName = res.getString("LastName");
// Close ResultSet
res.close();
sta.close();
con.close();
} catch (Exception e) {
System.err.println("Exception: "+e.getMessage());
}
}
}
Run this program to see the error if res.next() is not called after executeQuery():
Exception: Invalid operation at current cursor position.
