How to retrieve data from excel file using symfony2 excelbundle?

For a school project, I have to collect data from an Excel file uploaded by the user. I am using Symfony2 and have installed a bundle I found on knpbundles, named ExcelBundle. I read that to collect data with it from an Excel file, I should use the createWriter method of my phpExcel object. That is what I have done as shown below.

public function addContactsFromExcelAction(Request $request) {
    $uploadDir = '/var/www'.$request->getBasePath().'/uploads/';
    //die(var_dump($uploadDir));
    $file = $request->files->get('fichierExcel');
    $fileName = $file->getClientOriginalName();
    $fileSaved = $file->move($uploadDir,$fileName);
    $phpExcelObject = $this->get('phpexcel')->createPHPExcelObject($uploadDir.$fileName);
    $writer = $this->get('phpexcel')->createWriter($phpExcelObject, 'Excel2007');

}

But the thing is that actually, I do not really know how to use the writer to collect data from the cells of my excel datasheets.

Please, could anyone give me the trick to achieve my goal ?