accessing excel file stored in KM

Hi,

I'm developing web dynpro java application for nw portal 7.0.

I'm using jxl.jar for excel operations.

The command below gets error message.

What must i do to access document stored into KM?

Regards.

Code

Workbook wb = Workbook.getWorkbook(new File("/documents/X/abc.xls"));

Error message

java.io.FileNotFoundException: \documents\X\abc.xls (The system cannot find the path specified)