Apache POI Overview

Many a time, a software application is required to generate reports in Microsoft Excel file format. Sometimes, an application is even expected to receive Excel files as input data. For example, an application developed for the Finance department of a company will be required to generate all their outputs in Excel.

Any Java programmer who wants to produce MS Office files as output must use a predefined and read-only API to do so.

What is Apache POI?

Apache POI is a popular API that allows programmers to create, modify, and display MS Office files using Java programs. It is an open source library developed and distributed by Apache Software Foundation to design or modify Microsoft Office files using Java program. It contains classes and methods to decode the user input data or a file into MS Office documents.

Components of Apache POI

Apache POI contains classes and methods to work on all OLE2 Compound documents of MS Office. The list of components of this API is given below.

• POIFS (Poor Obfuscation Implementation File System) : This component is the basic factor of all other POI elements. It is used to read different files explicitly.
• HSSF (Horrible Spreadsheet Format) : It is used to read and write xls format of MS-Excel files.
• XSSF (XML Spreadsheet Format) : It is used for xlsx file format of MS-Excel.
• HPSF (Horrible Property Set Format) : It is used to extract property sets of the MS-Office files.
• HWPF (Horrible Word Processor Format) : It is used to read and write doc extension files of MS-Word.
• XWPF (XML Word Processor Format) : It is used to read and write docx extension files of MS-Word.
• HSLF (Horrible Slide Layout Format) : It is used for read, create, and edit PowerPoint presentations.
• HDGF (Horrible DiaGram Format) : It contains classes and methods for MS-Visio binary files.
• HPBF (Horrible PuBlisher Format) : It is used to read and write MS-Publisher files.

This tutorial guides you through the process of working on Excel files using Java. Therefore the discussion is confined to HSSF and XSSF components.
Note : Older versions of POI support binary file formats such as doc, xls, ppt, etc. Version 3.5 onwards, POI supports OOXML file formats of MS-Office such as docx, xlsx, pptx, etc.
Like Apache POI, there are other libraries provided by various vendors for Excel file generation. These include Aspose cells for Java by Aspose, JXL by Commons Libraries, and JExcel by Team Dev.