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The Apache Commons project differs from many other Apache hosted projects because it is comprised of multiple, independently released packages. This page provides an overview of the Commons components that are currently available.

Released Components

BCEL Byte Code Engineering Library - analyze, create, and manipulate Java class files
BeanUtils Easy-to-use wrappers around the Java reflection and introspection APIs.
BSF Bean Scripting Framework - interface to scripting languages, including JSR-223
CLI Command Line arguments parser.
Codec General encoding/decoding algorithms (for example phonetic, base64, URL).
Collections Extends or augments the Java Collections Framework.
Compress Defines an API for working with tar, zip and bzip2 files.
Configuration Reading of configuration/preferences files in various formats.
Crypto A cryptographic library optimized with AES-NI wrapping Openssl or JCE algorithm implementations
CSV Component for reading and writing comma separated value files.
Daemon Alternative invocation mechanism for unix-daemon-like java code.
DBCP Database connection pooling services.
DbUtils JDBC helper library.
Digester XML-to-Java-object mapping utility.
Email Library for sending e-mail from Java.
Exec API for dealing with external process execution and environment management in Java.
FileUpload File upload capability for your servlets and web applications.
Geometry Space and coordinates.
Imaging (previously called Sanselan) A pure-Java image library.
IO Collection of I/O utilities.
JCI Java Compiler Interface
JCS Java Caching System
Jelly XML based scripting and processing engine.
Jexl Expression language which extends the Expression Language of the JSTL.
JXPath Utilities for manipulating Java Beans using the XPath syntax.
Lang Provides extra functionality for classes in java.lang.
Logging Wrapper around a variety of logging API implementations.
Math Lightweight, self-contained mathematics and statistics components.
Net Collection of network utilities and protocol implementations.
Numbers Number types (complex, quaternion, fraction) and utilities (arrays, combinatorics).
Pool Generic object pooling component.
RNG Implementations of random numbers generators.
SCXML An implementation of the State Chart XML specification aimed at creating and maintaining a Java SCXML engine. It is capable of executing a state machine defined using a SCXML document, and abstracts out the environment interfaces.
Statistics Statistics.
Text Apache Commons Text is a library focused on algorithms working on strings.
Validator Framework to define validators and validation rules in an xml file.
VFS Virtual File System component for treating files, FTP, SMB, ZIP and such like as a single logical file system.
Weaver Provides an easy way to enhance (weave) compiled bytecode.

Elsewhere at Apache

The following components were part of Apache Commons but have moved elsewhere:

  • Cactus: Cactus is a simple test framework for unit testing server-side java code (Servlets, EJBs, Tag Libs, Filters, ...). The intent of Cactus is to lower the cost of writing tests for server-side code.
  • HiveMind: HiveMind is a services and configuration microkernel. HiveMind allows you to create your application using a service oriented architecture.
  • HttpClient 3.x: Framework for working with the client-side of the HTTP protocol.
  • Naming: The Naming subproject will contain common JNDI code along with various JNDI providers.