To read an excel file with GEL, you will need to leverage the poi.apache.org library either HSSF or XSSF classes depending on the excel format -- xls vs xlsx.
The HSSFWorkbook and XSSFWorkbook class constructors accept a java.io.InputStream so you will need to get the file_contents (Dave's post) into an inputstream.
So on your query against clb_dms_file_store, just get the file_contents blob from the queried resultset and once you have the blog you can pass the an inputstream via the getBinaryStream method on the blob.
V/r,
Gene