viewing from jtable

[egbai mmumene]

how do i view files with jtable been recieving an error here is the code.

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package sm.main;
import java.sql.*;
import javax.swing.table.AbstractTableModel;
/**
 *
 * @author smile
 */
public class TableModel extends AbstractTableModel{
private Connection connection;
private Statement stat;
private ResultSet rs;
private ResultSetMetaData rmd;
private int numberOfRows;
private boolean connectedToDatabase = false;
public TableModel(String driver, String url, String username, String password, String query)
throws SQLException, ClassNotFoundException
{
    Class.forName(driver);
connection = DriverManager.getConnection(url, username, password);
stat = connection.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);        
connectedToDatabase = true;
}
public Class getColumnClass( int column ) throws IllegalStateException
{
    if ( !connectedToDatabase )
 throw new IllegalStateException( "Not Connected to Database" );
    try{
        String className = rmd.getColumnClassName(column + 1);
        return Class.forName(className);
    }
    catch(Exception e){
        e.printStackTrace();
    }
    return Object.class;
}
    public int getRowCount() throws IllegalStateException{
        if(!connectedToDatabase)
        throw new IllegalStateException("Not connected");
    return numberOfRows;
    }

    public int getColumnCount() throws IllegalStateException{
       if(!connectedToDatabase) 
        throw new IllegalStateException("Not connected");
       try{
           return rmd.getColumnCount();
       }
       catch(SQLException sql){
           sql.printStackTrace();
       }
    return 0;
    }
   public String getColumnName(int column)throws IllegalStateException
 {
 if ( !connectedToDatabase )
 throw new IllegalStateException( "Not Connected to Database" );
try{
 return rmd.getColumnName( column + 1 );
}
 catch ( SQLException sqlException )
 {
sqlException.printStackTrace();
 } // end catch
return "";} 

    public Object getValueAt(int row, int column) {
    if(!connectedToDatabase)    
        throw new IllegalStateException("Not connected");
    try{
        rs.absolute(row + 1);
        return rs.getObject(column + 1);
        }
    catch(SQLException sqlException){
        sqlException.printStackTrace();
    }
    return"";
    }
public void setQuery(String query)
        throws SQLException, IllegalStateException
{
  if(!connectedToDatabase)
      throw new IllegalStateException("");
  rs = stat.executeQuery(query);
  rmd = rs.getMetaData();
  rs.last();
  numberOfRows = rs.getRow();
  fireTableStructureChanged();
  
}
public void disconnect(){
    if(connectedToDatabase){
        try{
            rs.close();
            stat.close();
            connection.close();
        }
     catch(SQLException sqlException){
        sqlException.printStackTrace();
    }
        finally{
            connectedToDatabase = false;
        }
    }
        
}
}

and here is the errorrun:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at sm.main.TableModel.getColumnCount(TableModel.java:50)
at javax.swing.JTable.createDefaultColumnsFromModel(JTable.java:1290)
at javax.swing.JTable.tableChanged(JTable.java:4389)
at javax.swing.JTable.setModel(JTable.java:3691)
at javax.swing.JTable.<init>(JTable.java:633)
at javax.swing.JTable.<init>(JTable.java:574)
at sm.main.moviemethod.view(moviemethod.java:110)
at sm.main.movie$2.actionPerformed(movie.java:69)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.AbstractButton.doClick(AbstractButton.java:376)
at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:833)
at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(BasicMenuItemUI.java:877)
at java.awt.Component.processMouseEvent(Component.java:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2713)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:707)
at java.awt.EventQueue.access$000(EventQueue.java:101)
at java.awt.EventQueue$3.run(EventQueue.java:666)
at java.awt.EventQueue$3.run(EventQueue.java:664)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:680)
at java.awt.EventQueue$4.run(EventQueue.java:678)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:677)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
BUILD STOPPED (total time: 36 seconds)

[K. Tsang]

So you are trying to use a TableModel to get the columns/rows in the database table?

From you error print stack, it looks like "line 50" of your class got a NullPointerException. And I reckon it's the ResutlMetaData variable rmd is null.

How are you getting the necessary info for your meta data?

[egbai mmumene]

i got the TableModel example from a book please what do you suggest i do.

[Rob Spoor]

Did you call setQuery before applying the model to a JTable? Did this method throw an exception you ignored?

[egbai mmumene]

I used the setQuery method in an ActionListener overide method, so when a user presses a button it will bring up the table contents of that button. Or should i declare an inner class from the button?

[Rob Spoor]

Well, you currently set the table model before it's properly initialized. You should check not only if there is a database connection, but also if the result set meta data is set. You also shouldn't throw an exception if that occurs because you'll just replace your NullPointerExceptions with other ones. Instead return some defaults - 0 rows, 0 columns, null for getColumnClass and getValueAt.

[egbai mmumene]

The error has stopped showing after removing the throw exception. But an empty frame opens with no values in it or GUI objects in it

[egbai mmumene]

Please help

[Paul Clapham]

Sorry, you're going to have to explain what "removing the throw exception" means and also what code you have now.