Apache POI, a project run by the Apache Software Foundation, and previously a sub-project of the Jakarta Project, provides pure Java libraries for reading and writing files in Microsoft Office formats, such as Word, PowerPoint and Excel.

History and roadmap

The name was originally an acronym for "Poor Obfuscation Implementation" , referring humorously to the fact that the file formats seemed to be deliberately obfuscated, but poorly, since they were successfully reverse-engineered. This expansion - and those of the similar names for the various sub-projects - were removed from the official web-pages in order to better market the tools to businesses who would not consider such humour appropriate. The authors also noted the existence of the Hawaiian dish named poi, made of mashed taro root, which had similarly derogatory connotations.

Architecture

The Apache POI project contains the following subcomponents:

POIFS (Poor Obfuscation Implementation File System) - This component reads and writes Microsoft's OLE 2 Compound document format. Since all Microsoft Office files are OLE 2 files, this component is the basic building block of all the other POI elements. POIFS can therefore be used to read a wider variety of files, beyond those whose explicit decoders are already written in POI.

HSSF (Horrible SpreadSheet Format) - reads and writes Microsoft Excel (XLS) format files. It can read files written by Excel 97 onwards; this file format is known as the BIFF 8 format. As the Excel file format is complex and contains a number of tricky characteristics, some of the more advanced features of can not be read. For example, POI is unable to open spreadsheets that have filters or views .

HPSF (Horrible Property Set Format) - reads "Document Summary" information from Microsoft Office files. This is essentially the information that one can see by using the File|Properties menu item within an Office application.

HWPF (Horrible Word Processor Format) - aims to read and write Microsoft Word 97 (DOC) format files. This component is in initial stages of development.

HSLF (Horrible Slide Layout Format) - is a pure Java implementation for Microsoft Powerpoint files. This provides a limited ability to read and edit presentations and it is presently in the initial stages of development.

Currently (as of March, 2007), and other than the base POIFS component, the HSSF component is the more advanced feature of the library . The other components (HPSF, HWPF, and HSLF) are in a working stage but still in early level of development

The POI library is also provided as a Ruby extension.