if(userName == null || url == null || driverClass == null) { return null; }
	public Connection connect( String userName, String password, String url,			String driverClass, String odaDriverName )	{		if(!userName.equals(this.userName) ||  !url.equals(this.url) || !driverClass.equals(this.driverClass))		{			if(jdbcConnection != null)			{				closeConnection();				jdbcConnection = null;				metaData = null;			}					}		if(jdbcConnection == null)		{			String additionalClassPath = JdbcToolKit.getJdbcDriverClassPath( odaDriverName );					try			{				jdbcConnection = DriverLoader.getConnection( driverClass,						additionalClassPath,						url,						userName,						password );				if ( jdbcConnection == null )				{					MessageDialog.openError( PlatformUI.getWorkbench( )							.getDisplay( )							.getActiveShell( ),							JdbcPlugin.getResourceString("connection.test"),//$NON-NLS-1$							JdbcPlugin.getResourceString("connection.failed"));//$NON-NLS-1$				}				else				{				    this.driverClass = driverClass;				    this.url = url;				    this.userName = userName;				    this.password = password;				}			}			catch ( SQLException e )			{				e.printStackTrace( );			}					}		return jdbcConnection;	}