Composite Cell in a gwt application

I am trying to create a CompositeCell which consists of a TextCell and a ButtonCell. I want to add the CompositeCell to Column ordinarily and then the Column to a CellTable. However I am not able to figure out how the instance of the column should be. In particular I cannot find its type parameters in the following code:

 Column<FilterInfo, ?> compositeColumn = new Column<FilterInfo, ?>(createCompositeCell()) {

  @Override
  public Object getValue(Object object) {
    // TODO Auto-generated method stub
    return null;
  }}; 

The method which creates the CompositeCell of the custom class FilterInfo (is it necessary?) is:

private CompositeCell<FilterInfo> createCompositeCell(){

HasCell<FilterInfo, String> filterName = new HasCell<FilterInfo, String>() {

  public Cell<String> getCell() {
    return new TextCell();
  }

  public FieldUpdater<FilterInfo, String> getFieldUpdater() {
    // TODO Auto-generated method stub
    return null;
  }

  public String getValue(FilterInfo object) {
    return object.getFilterName();
  }};

  HasCell<FilterInfo, String> filterButton = new HasCell<FilterInfo,String>(){

    public Cell<String> getCell() {
      return new ButtonCell();
    }

    public FieldUpdater<FilterInfo, String> getFieldUpdater() {
      // TODO Auto-generated method stub
      return null;
    }

    public String getValue(FilterInfo object) {
      // TODO Auto-generated method stub
      return "...";
    }
  };

  List<HasCell<FilterInfo, ?>> cells = new ArrayList<HasCell<FilterInfo, ?>>();
  cells.add(filterName);
  cells.add(filterButton);

  CompositeCell<FilterInfo> compositeCell = new CompositeCell<FilterInfo>(cells);

  return compositeCell;

}

I would be grateful by any indication to adapt the code or another suggestion to create the desired CompositeCell and to add it to the CellTable properly.

Do you have to use a composite cell? To me this seems like a lot of work, and it may be a lot easier to just create your own custom cell.

Have a read of the documentation on Creating Custom Cells