Microsoft Office Programing With POI

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.

The name POI stands for Poor Obfuscation Implementation, referring 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 POI consists of APIs for manipulating various file formats based upon Microsoft's OLE 2 Compound Document Format using pure Java. Almost all Microsoft Office files like Microsoft Excel, Microsoft Word, Microsoft Power Point, Microsoft Visio Documents etc follows the OLE 2 Compound Document Format. But the new Office 2007 formats like .xlsx, .docx, .pptx etc are not based on the OLE 2 Compound Document Format hense POI doesn't have the capability to read or write these types of documents. But work is in progress to accomodate these types of documents. POI has the following components to read and write the Microsoft's OLE 2 Compound Document Format based files.

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.

We can think of POIFS as a "zip" library. Once we get the data in a zip file we still need to interpret the data. As a general rule, while all of our formats use POIFS, most of them attempt to abstract you from it.

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 cannot be read.

XSSF (XML SpreadSheet Format) – reads and writes Microsoft Excel OOXML (XLSX) format files – 3.5 branch only. Similar feature set to HSSF, but for Office Open XML files.

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.

HSLF (Horrible Slide Layout Format) – is a pure Java implementation for Microsoft PowerPoint files. This provides the ability to read, create and edit presentations

HDGF (Horrible DiaGram Format) – is an initial pure Java implementation for Microsoft Visio binary files. It provides an ability to read the low level contents of the files.