| Attributes | Runtime API to metadata attributes such as doclet tags. 类属性运行时API，类似文档生成工具（doclet标签）。 |
| BCEL | Byte Code Engineering Library - analyze, create, and manipulate Java class files 字节编码处理包 - 分析、创建、操作java类文件。 |
| BeanUtils | Easy-to-use wrappers around the Java reflection and introspection APIs. 容易使用的bean处理工具，大量使用java反射和内省实现。 |
| Betwixt | Services for mapping JavaBeans to XML documents, and vice versa. JavaBeans与XML的相互转换工具。 |
| BSF | Bean Scripting Framework - interface to scripting languages, including JSR-223 Bean脚本框架：脚本语言接口，包括JSR-223。 |
| Chain | Chain of Responsibility pattern implemention. 责任链模式实现类库 |
| CLI | Command Line arguments parser. 命令行参数解析器。 |
| Codec | General encoding/decoding algorithms (for example phonetic, base64, URL). 常用加解密算法，如：语音、base64、url |
| Collections | Extends or augments the Java Collections Framework. Java集合扩展包。 |
| Compress | Defines an API for working with tar, zip and bzip2 files. Tar、zip、bzip2等格式压缩解压工具包。 |
| Configuration | Reading of configuration/preferences files in various formats. 文件配置读取工具包。 |
| 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. |
| Discovery | Tools for locating resources by mapping service/reference names to resource names. |
| EL | Interpreter for the Expression Language defined by the JSP 2.0 specification. |
| 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. |
| Functor | A functor is a function that can be manipulated as an object, or an object representing a single, generic function. |
| 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. |
| Launcher | Cross platform Java application launcher. |
| Logging | Wrapper around a variety of logging API implementations. |
| Math | Lightweight, self-contained mathematics and statistics components. |
| Modeler | Mechanisms to create Model MBeans compatible with JMX specification. |
| Net | Collection of network utilities and protocol implementations. |
| OGNL | An Object-Graph Navigation Language |
| Pool | Generic object pooling component. |
| Primitives | Smaller, faster and easier to work with types supporting Java primitive types. |
| Proxy | Library for creating dynamic proxies. |
| 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. |
| Transaction | Implementations for multi level locks, transactional collections and transactional file access. |
| 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. |
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