Vaadin Table with Checkboxes

myTable = new Table();
myTable.addContainerProperty("c1", Boolean.class, null);
myTable.setColumnCollapsed("c1", true);
myTable.addGeneratedColumn("chk1", new ColumnGenerator() {

    @Override
    public Object generateCell(Table source, final Object itemId, Object columnId) {
        Property prop = source.getItem(itemId).getItemProperty("c1");//columnId
        final CheckBox cb = new CheckBox(null, prop);
        cb.setImmediate(true);
        cb.addListener(new Property.ValueChangeListener() {
            @Override
            public void valueChange(Property.ValueChangeEvent event) {
                if (myTable.getContainerProperty(itemId, "field").getValue() != null) {
                    if (!myTable.getContainerProperty(itemId, "field").getValue().equals("") && !myTable.getContainerProperty(itemId, "field").getValue().equals("0")) {
                        System.out.println("qta_prel:"+myTable.getContainerProperty(itemId, "field").getValue());
                    } else {
                        cb.setValue(null);
                        getWindow().showNotification("Type something", Window.Notification.TYPE_ERROR_MESSAGE);
                    }
                }
            }
        });
        return cb;
    }
});
myTable.addContainerProperty("field", String.class, null);

// insert on table
myTable.addItem(new Object[] { rs.getBoolean("chk1"), rs.getString("field") }, null);