Inputting data from database to a JTable

Question

hi. i'm having this problem of putting data collected from a database into a JTable for presentation. here is my code...can anyone please tell me what's wrong? the more i look at the code the more i want to give up...help would be much appreciated...
            colCount = 0;
            rowCount = 0;
            try
               Connection conn = newDB.getconnection();
                DatabaseMetaData meta = conn.getMetaData();
                //get tables from the metadata
                ResultSet metaResults = meta.getTables(null, null, null, new String[] {"TABLE"});
                while(metaResults.next())
                    String table = metaResults.getString(3);
                    String query = "SELECT * FROM " + table;
                    ResultSet result = stat.executeQuery(query);
                    //prints the column names
                    ResultSetMetaData metaData = result.getMetaData();
                    int columnCount = metaData.getColumnCount();
                    colCount = metaData.getColumnCount();
                    result.last();
                    rowCount = result.getRow();
                    result.first();
                    colNames = new String[colCount];
                    tableData = new String[rowCount][colCount];
                    for (int i = 1; i <= columnCount; i++)
                        if (i > 1)
                            gui.txtArea.append(", ");
                        colNames[i-1] = metaData.getColumnLabel(i);
                        gui.txtArea.append(metaData.getColumnLabel(i));
                    gui.txtArea.append("\n");
                    int j=0;
                    //print out the records
                    while (result.next())
                        for (int i = 1; i <= columnCount; i++)
                            tableData[j][i-1] = result.getString(i);
                            if (i > 1) gui.txtArea.append(", ");
                            gui.txtArea.append(result.getString(i));
                        gui.txtArea.append("\n");
                        j++;
                    result.close();
                //close the result set
                metaResults.close();
            catch(Exception exp){ exp.getMessage();}and the code to print the table:
JTable table = new JTable(tableData, colNames);
            JScrollPane scrollPane = new JScrollPane(table);
            JFrame frame = new JFrame();
            frame.getContentPane().add(frame,"Center");
            frame.setSize(200,200);
            frame.setVisible(true);here's a little explanation of the code. i'm trying to get the column names into the colNames[] array (string) and the records into the tableData[][](String) to fill up the table. but what i've noticed is that when i used the result.getRow() and result.last() and result.first() methods, the table information wont print out the data in the textarea, (which it would without those two methods). i dont mind if it doesnt display it on the text area. my main problem is that there is a null pointer exception when i tried to display the table...
please tell me if you're confused about the code and i'll try my best to give further explanations...thx
khine

Answer 1

In order to work, your table needs a model:
DefaultTableModel m = new DefaultTableModel();
table.setModel(d);Next, you have to add columns and lines in your model (not in the table)
d.addColumn(colNames);
and
d.addRow(tableData);
Sorry to say, but this approach is a little bit MFC like.
First, java is model-view-controller. Think about you have millions of records in your database, then you will feel the GUI memory with millions of enties that will be never used.
So, I recommend you first to open a scrollable cursor:
            PreparedStatement s1 = c.prepareStatement("select * from clients",
                    ResultSet.TYPE_SCROLL_INSENSITIVE , ResultSet.CONCUR_READ_ONLY);Extend the AbstractTableModel class, and return dynamically the information
the render needs:
  public int getRowCount();
  public int getColumnCount();
  public Object getValueAt(int row, int column);getColumnCount is the number of columnsin the cursor
getRowCount you get by going to last record in cursor, then ask the position of the record (getRow and last of RecordSet)
getValueAt(row, column) - fetch the entry "row" and return the data at "column" position.