Apache commons——Apache旗下的通用工具包项目

Apache Commons是Apache旗下的一个开源项目，包含了很多开源的工具，用于解决平时编程经常会遇到的问题，减少重复劳动

这里是Apache commons的官方网站

下面是工具的简单介绍：

Components AttributesRuntime API to metadata attributes such as doclet tags.BCELByte Code Engineering Library - analyze, create, and manipulate Java class filesBeanUtils针对java bean的工具集，对bean进行了很多包装，可以方便地对bean进行操作，有关java bean的情况参看这里Betwixt用来将javabean映射为xml文件以及将xml文件映射回javabeanChainChain of Responsibility pattern implemention.CLI用于解析命令行参数的工具Codec用来编码和解码，包括Base64，URL，Soundx等等CollectionsJava Collections类的拓展， collections是java.util包下的一个类，包括有关集合的操作mpressDefines an API for working with tar, zip and bzip2 files.Configuration用来帮助处理配置文件，支持多种存储方式（propertities,xml,plist,JDBC等等）DaemonAlternative invocation mechanism for unix-daemon-like java code.DBCPDatabase connection pooling services.DbUtils简化JDBC的数据库操作Digesterxml和java对象间的映射DiscoveryTools for locating resources by mapping service/reference names to resource names.ELInterpreter for the Expression Language defined by the JSP 2.0 specification.Email发送email的方法ExecAPI for dealing with external process execution and environment management in Java.FileUploadFile upload capability for your servlets and web applications.IOIO方法的集合，可以看为java.io包的扩展JCIJava Compiler InterfaceJCSJava Caching SystemJellyXML based scripting and processing engine.JexlExpression language which extends the Expression Language of the JSTL.JXPath用XPath的方法查看javabean，有关XPath的情况看这里LangProvides extra functionality for classes in java.lang.LauncherCross platform Java application launcher.LoggingWrapper around a variety of logging API implementations.MathLightweight, self-contained mathematics and statistics components.ModelerMechanisms to create Model MBeans compatible with JMX specification.NetCollection of network utilities and protocol implementations.PoolGeneric object pooling component.PrimitivesSmaller, faster and easier to work with types supporting Java primitive types.ProxyLibrary for creating dynamic proxies.SanselanA pure-Java image library.SCXMLAn 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.TransactionImplementations for multi level locks, transactional collections and transactional file access.ValidatorFramework to define validators and validation rules in an xml file.VFSVirtual File System component for treating files, FTP, SMB, ZIP and such like as a single logical file system.

ps:原来在commons项目中的httpclient组件现在变为 Apache HttpComponents的一部分

参考：

http://commons.apache.org/index.html

http://www.cnblogs.com/jackyrong/archive/2006/10/15/529599.html