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在Java社区，有那么一小撮人，觉得Java API还不足用，至少还不够好用，就起了给增强Java API的念头，于是Apache Commons项目诞生了。为了便于被使用，Apache Commons项目采用了与Java API的包一致的方式组织，于是出现了一系列子项目。
伴随着Apache Commons项目的发展，有些子项目保持了顽强的生命力，而有些则慢慢沦为弃子，还有些新的子项目不断产生。于是，Apache Commons项目首先被分为如下3个独立的组件库：
事实上，大家开发过程中，通常能够想起来的都属于Apache Commons Proper库，这也是我们后续要讨论的库。所以，默认提到Apache Commons项目都是指Apache Commons Proper库中的组件。
Apache Commons Proper库中的组件都是以子项目的形式组织，列表如下：
| Components | Description | Latest Version | Released |
|---|---|---|---|
| Byte Code Engineering Library - analyze, create, and manipulate Java class files | 6.2 | 2017-11-08 | |
| Easy-to-use wrappers around the Java reflection and introspection APIs.为Java Bean的动态属性（运行时才确定的属性）提供getter/setter方法。主要工具类：PropertyUtils（推荐），BeanUtils | 1.9.3 | 2016-09-26 | |
| Bean Scripting Framework - interface to scripting languages, including JSR-223 | 3.1 | 2010-06-24 | |
| Chain of Responsibility pattern implemention. | 1.2 | 2008-06-02 | |
| Command Line arguments parser. | 1.4 | 2017-03-09 | |
| General encoding/decoding algorithms (for example phonetic, base64, URL). | 1.11 | 2017-10-20 | |
| Extends or augments the Java Collections Framework. | 4.1 | 2015-11-27 | |
| Defines an API for working with tar, zip and bzip2 files. | 1.17 | 2018-06-03 | |
| Reading of configuration/preferences files in various formats. | 2.2 | 2017-10-12 | |
| A cryptographic library optimized with AES-NI wrapping Openssl or JCE algorithm implementations. | 1.0.0 | 2016-07-22 | |
| Component for reading and writing comma separated value files. | 1.5 | 2017-09-03 | |
| Alternative invocation mechanism for unix-daemon-like java code. | 1.0.15 | 2013-04-03 | |
| Database connection pooling services. | 2.3.0 | 2018-05-12 | |
| JDBC helper library. | 1.7 | 2017-07-20 | |
| XML-to-Java-object mapping utility. | 3.2 | 2011-12-13 | |
| Library for sending e-mail from Java. | 1.5 | 2017-08-01 | |
| API for dealing with external process execution and environment management in Java. | 1.3 | 2014-11-06 | |
| File upload capability for your servlets and web applications. | 1.3.3 | 2017-06-13 | |
| A functor is a function that can be manipulated as an object, or an object representing a single, generic function. | 1.0 | 2011-??-?? | |
| Space and coordinates. | 1.0 | 2018-??-?? | |
| A pure-Java image library. | 0.97-incubator | 2009-02-20 | |
| Collection of I/O utilities. | 2.6 | 2017-10-15 | |
| Java Compiler Interface | 1.1 | 2013-10-14 | |
| Java Caching System | 2.2 | 2017-08-02 | |
| XML based scripting and processing engine. | 1.0.1 | 2017-09-27 | |
| Expression language which extends the Expression Language of the JSTL. | 3.1 | 2017-04-14 | |
| Utilities for manipulating Java Beans using the XPath syntax. | 1.3 | 2008-08-14 | |
| Provides extra functionality for classes in java.lang.Lang 3.0开始使用commons-lang3的构件名称。主要工具类：StringUtils， ArrayUtils | 3.7 | 2017-11-08 | |
| Wrapper around a variety of logging API implementations. | 1.2 | 2014-07-11 | |
| Lightweight, self-contained mathematics and statistics components. | 3.5 | 2015-04-17 | |
| Collection of network utilities and protocol implementations. | 3.6 | 2017-02-15 | |
| Number types (complex, quaternion, fraction) and utilities (arrays, combinatorics). | 1.0 | 2017-??-?? | |
| An Object-Graph Navigation Language | 4.0 | 2013-??-?? | |
| Generic object pooling component. | 2.5.0 | 2017-12-19 | |
| Library for creating dynamic proxies. | 1.0 | 2008-02-28 | |
| Common implementation of RDF 1.1 that could be implemented by systems on the JVM. | 0.3.0-incubating | 2016-11-15 | |
| Implementations of random numbers generators. | 1.0 | 2016-12-13 | |
| 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. | 0.9 | 2008-12-01 | |
| Statistics. | 0.1 | ????-??-?? | |
| Apache Commons Text is a library focused on algorithms working on strings.处理文本（非字符串） | 1.3 | 2018-03-21 | |
| Framework to define validators and validation rules in an xml file. | 1.6 | 2017-02-21 | |
| Virtual File System component for treating files, FTP, SMB, ZIP and such like as a single logical file system. | 2.2 | 2017-10-06 | |
| Provides an easy way to enhance (weave) compiled bytecode. | 1.3 | 2016-10-18 |
参考链接：
http://commons.apache.org/
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