Apache POI

Java | Excel API | Document automation | Microsoft Office formats | OpenXML
Apache POI is a powerful, open-source Java library for editing Microsoft Office documents. The name POI stands for “Poor Obfuscation Implementation”, which was originally a dig at the complicated structure of proprietary formats. Today, Apache POI is an established tool for developers who want to programmatically create, read, change or export Office files such as Excel, Word or PowerPoint documents.
A central element of the library is the support of Microsoft Office Binary File Formats (OLE2) as well as the more modern Office Open XML formats (OOXML). This means that Apache POI covers both old .xls and .doc files as well as current .xlsx and .docx files. Two main components are available for Excel files: HSSF for the older binary format (.xls) and XSSF for the XML-based format (.xlsx). HWPF and XWPF serve as equivalents for Word documents.
The library offers a wide range of functions, including the insertion of text, formatting, tables, diagrams and even embedded images. Apache POI is particularly popular in data processing and report creation, for example for the automated generation of Excel evaluations or for integration into company applications in which structured data is to be exported as Office documents.
A major advantage of Apache POI is its complete integration into Java projects without additional dependence on Microsoft software or libraries. This makes POI ideal for server-side applications, for example in web services, backend systems or microservices architectures.
In combination with other technologies such as Spring Boot, Apache Maven or JasperReports, complex workflows for document generation or processing can be realized. Apache POI is therefore an indispensable tool for developers who want to build data-driven applications with a high degree of document automation.
Compared to alternative libraries such as JExcelAPI or Aspose, Apache POI scores points with its open source license, continuous further development by the Apache Foundation and broad community support.
The experts at BITS have used Apache POI and related technologies in a large number of projects. A selection of case studies and references can be found below.