How to get Database information properly to JTable...

Question

Hi!
Sorry to bother with this kind of stupid question but I thought I'd ask someone for help in here...
The case is that I'm trying to learn the use of Swing components at the moment, and I had this strange idea of trying to add my databases to this study. So, I started testing with the sample codes included in java.sun.com's pages...
I got the data from the database to Jtable. The problem is that at the moment this attempt creates the table in the same loop as it gets the data from the database so I get every row of data to a separate table... :)
So, if someone could help me in my studies and tell how can I get my data to a single table? :)
Here's what I've been messing with...
try
yhteys=DriverManager.getConnection(url, tunnus, salasana);
stmt=yhteys.createStatement();
sql = "SELECT A.Asiakasnumero, A.Yritys, A.L?hiosoite, A.Postinumero, A.Postitoimipaikka, T.Tilnro, T.Toipvm, T.Tuotenumero, T.Tuote, T.Kappaletta FROM ASIAKAS AS A, TILAUS AS T, TUOTE AS TU WHERE Toipvm=(SELECT MAX(Toipvm) FROM TILAUS AS TI WHERE TI.Asnro=T.Asnro) AND A.Asiakasnumero=T.Asnro AND T.Tuotenumero=TU.Tuotenro AND A.Asiakasnumero=1";
ResultSet rs=stmt.executeQuery(sql);
while(rs.next())
Object an=rs.getString("Asiakasnumero");
Object yr=rs.getString("Yritys");
Object lo=rs.getString("L?hiosoite");
Object pn=rs.getString("Postinumero");
Object pt=rs.getString("Postitoimipaikka");
Object tn=rs.getString("Tilnro");
Object tp=rs.getDate("Toipvm");
Object tu=rs.getString("Tuotenumero");
Object tt=rs.getString("Tuote");
Object ka=rs.getString("Kappaletta");
String[] columnNames = {"Asiakasnumero",
          "Yritys",
          "L?hiosoite",
          "Postinumero",
          "Postitoimipaikka",
          "Tilnro",
          "Toipvm",
          "Tuotenumero",
          "Tuote",
          "Kappaletta"};
Object[][] data = {
{an, yr, lo, pn, pt, tn, tp, tu, tt, ka},
final JTable table = new JTable(data, columnNames);
table.setPreferredScrollableViewportSize(new Dimension(1000, 70));
if (DEBUG) {
table.addMouseListener(new MouseAdapter() {
public void mouseClicked(MouseEvent e) {
printDebugData(table);
JScrollPane scrollPane = new JScrollPane(table);
add(scrollPane);
stmt.close();
yhteys.close();
catch(SQLException ex)
System.err.println("SQLException: "+ex.getMessage());
As you can see, this is EXTREMELY raw version (all data is retrieved as Strings instead of what they really are, and... Well... The JTable part is quite a straight copy from "Simple Table Demo"...).
This is because I wanted to have the table running first before trying anything else and I'm learning from these examples. So, if anyone of you could give me hints I would really appreciate them...
What I need to do first is get the JTable-part away from the while loop but how does that happen? :D
/Sampsa

Answer 1

You need to have layers. A layer is one or more classes that exist to provide a specific functionality. Typically a layer is "between" to other things and each thing can send input and get output from the layer.
The gui layer does the gui part. (The two sides are the 'user' and the 'database layer')
The database part does the database part. (The two sides are the 'gui layer' and the 'database')
The gui layer calls the database layer to do the work.
So for example you would have the following method in the database layer.
Customer.getByName(String firstName, String lastName)
This method would get a customer using the customer name to build the query string.
Now if you want the Customer object could just have a bunch of get methods to get the data after you call the above method....
getFirstName()
getLastName()
getAddress()
getTelephone()
The problem with the above becomes apparent when you start adding stuff, more types of objects and more fields to the objects.
So typically a DTO is used.....
http://java.sun.com/blueprints/corej2eepatterns/Patterns/TransferObject.html
Try reading through the above link and you might also look at this one....
http://java.sun.com/blueprints/corej2eepatterns/Patterns/DataAccessObject.html
Keep in mind that you don't necessarily need the details in the above but just focus on the conceptual ideas.
And once you read the above ask for more information.