HSSF is the POI Project's pure Java implementation of the Excel '97(-2002) file format.

HSSF provides a way to read spreadsheets create, modify, read and write XLS spreadsheets It provides:

• low level structures for those with special needs
• an eventmodel api for efficient read-only access
• a full usermodel api for creating, reading and modifying XLS files

Truth be told there is probably a better way to generate your spreadsheet generation (yet you'll still be using HSSF indirectly). At the time of this writing we're in the process of moving the HSSF Serializer over to the Apache Cocoon Project. With Cocoon you can serialize any XML datasource (of which might be a ESQL page outputting in SQL for instance) by simply applying the stylesheet and designating the serializer.

If you're merely reading spreadsheet data, then use the eventmodel api in the org.apache.poi.hssf.eventmodel package.

If you're modifying spreadsheet data then use the usermodel api. You can also generate spreadsheets this way, but using Cocoon (which will do it this way indirectly) is the best way...we promise.