Problem with mysql query from java

First I make a record to the database from a Frame and without leaving the application I enter another Frame where I consult the data but the data that I just entered from the previous Frame does not appear, if I close the program and I'll run it again and enter the Frame of the queries directly if I see the record, this is the code I use to make the query.

 try {
    DefaultTableModel modelo = new DefaultTableModel();
    final JTable table = new JTable(modelo);
    TableColumnModel columnModel = table.getColumnModel();

    for(int i=0;i<4;i++) {
        modelo.addColumn(columnas[i]);
    }
    columnModel.getColumn(0).setPreferredWidth(70);
    columnModel.getColumn(1).setPreferredWidth(120);
    columnModel.getColumn(2).setPreferredWidth(30);
    columnModel.getColumn(3).setPreferredWidth(30);

    DefaultTableCellRenderer tcr = new DefaultTableCellRenderer();
    tcr.setHorizontalAlignment(SwingConstants.CENTER);
    table.getColumnModel().getColumn(0).setCellRenderer(tcr);
    table.getColumnModel().getColumn(1).setCellRenderer(tcr);
    table.getColumnModel().getColumn(2).setCellRenderer(tcr);
    table.getColumnModel().getColumn(3).setCellRenderer(tcr);

    table.setPreferredScrollableViewportSize(new Dimension(400,300));
    JScrollPane scrollpane = new JScrollPane(table);

    Connection con = getConection();
    String sql = "SELECT num_control,Nombre,fecha_inicio,fecha_termino FROM alumno";
    ps = con.prepareStatement(sql);
    rs = ps.executeQuery();

    ResultSetMetaData rsMd = rs.getMetaData();
    int cantidadColumnas = rsMd.getColumnCount();

    while(rs.next()) {
        Object[] filas = new Object[cantidadColumnas];
        for(int i=0; i<cantidadColumnas;i++) {
            filas[i]=rs.getObject(i+1); 
        }
        modelo.addRow(filas);
    }