Java开发过程中的常用工具类库
Apache Commons类库
Apache?Commons是一个非常有用的工具包，为解决各种实际的问题提供了通用现成的代码，不需要我们程序员再重复造轮子。关于这个类库的详细介绍可以访问官网介绍。下面表格列出了部分的工具包。我们平时开发过程中可以根据自己的需要挑选合适的工具包。
| Components | Description | Latest Version | Released |
|---|---|---|---|
| BCEL | Byte Code Engineering Library - analyze, create, and manipulate Java class files | 6.3.1 | 2019/3/24 |
| BeanUtils | Easy-to-use wrappers around the Java reflection and introspection APIs. | 1.9.3 | 2016/9/26 |
| BSF | Bean Scripting Framework - interface to scripting languages, including JSR-223 | 3.1 | 2010/6/24 |
| Chain | Chain of Responsibility pattern implemention. | 1.2 | 2008/6/2 |
| CLI | Command Line arguments parser. | 1.4 | 2017/3/9 |
| Codec | General encoding/decoding algorithms (for example phonetic, base64, URL). | 1.12 | 2019/2/16 |
| Collections | Extends or augments the Java Collections Framework. | 4.3 | 2019/2/5 |
| Compress | Defines an API for working with tar, zip and bzip2 files. | 1.18 | 2018/8/16 |
| Configuration | Reading of configuration/preferences files in various formats. | 2.4 | 2018/10/29 |
| Crypto | A cryptographic library optimized with AES-NI wrapping Openssl or JCE algorithm implementations. | 1.0.0 | 2016/7/22 |
| CSV | Component for reading and writing comma separated value files. | 1.6 | 2018/9/25 |
| Daemon | Alternative invocation mechanism for unix-daemon-like java code. | 1.0.15 | 2013/4/3 |
| DBCP | Database connection pooling services. | 2.6.0 | 2019/2/19 |
| DbUtils | JDBC helper library. | 1.7 | 2017/7/20 |
| Digester | XML-to-Java-object mapping utility. | 3.2 | 2011/12/13 |
| Library for sending e-mail from Java. | 1.5 | 2017/8/1 | |
| Exec | API for dealing with external process execution and environment management in Java. | 1.3 | 2014/11/6 |
| FileUpload | File upload capability for your servlets and web applications. | 1.4 | 2019/1/16 |
| Functor | A functor is a function that can be manipulated as an object, or an object representing a single, generic function. | 1 | 2011-??-?? |
| Geometry | Space and coordinates. | 1 | 2018-??-?? |
| Imaging (previously called Sanselan) | A pure-Java image library. | 0.97-incubator | 2009/2/20 |
| IO | Collection of I/O utilities. | 2.6 | 2017/10/15 |
| JCI | Java Compiler Interface | 1.1 | 2013/10/14 |
| JCS | Java Caching System | 2.2,1 | 2018/8/23 |
| Jelly | XML based scripting and processing engine. | 1.0.1 | 2017/9/27 |
| Jexl | Expression language which extends the Expression Language of the JSTL. | 3.1 | 2017/4/14 |
| JXPath | Utilities for manipulating Java Beans using the XPath syntax. | 1.3 | 2008/8/14 |
| Lang | Provides extra functionality for classes in java.lang. | 3.9 | 2019/4/15 |
| Logging | Wrapper around a variety of logging API implementations. | 1.2 | 2014/7/11 |
| Math | Lightweight, self-contained mathematics and statistics components. | 3.5 | 2015/4/17 |
| Net | Collection of network utilities and protocol implementations. | 3.6 | 2017/2/15 |
| Numbers | Number types (complex, quaternion, fraction) and utilities (arrays, combinatorics). | 1 | 2017-??-?? |
| OGNL | An Object-Graph Navigation Language | 4 | 2013-??-?? |
| Pool | Generic object pooling component. | 2.6.2 | 2019/4/11 |
| Proxy | Library for creating dynamic proxies. | 1 | 2008/2/28 |
| RDF | Common implementation of RDF 1.1 that could be implemented by systems on the JVM. | 0.3.0-incubating | 2016/11/15 |
| RNG | Implementations of random numbers generators. | 1.2 | 2018/12/12 |
| 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. | 0.9 | 2008/12/1 |
| Statistics | Statistics. | 0.1 | ????-??-?? |
| Text | Apache Commons Text is a library focused on algorithms working on strings. | 1.6 | 2018/10/16 |
| Validator | Framework to define validators and validation rules in an xml file. | 1.6 | 2017/2/21 |
| VFS | Virtual File System component for treating files, FTP, SMB, ZIP and such like as a single logical file system. | 2.3 | 2019/2/4 |
| Weaver | Provides an easy way to enhance (weave) compiled bytecode. | 2 | 2018/9/7 |
除了上面表格中的工具包，Apache Common项目还包括以下几个工具包，其中的http-client是我们平时非常常用的。
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.
Guava类库
Guava工程包含了若干被Google的 Java项目广泛依赖 的核心库，例如：集合 [collections] 、缓存 [caching] 、原生类型支持 [primitives support] 、并发库 [concurrency libraries] 、通用注解 [common annotations] 、字符串处理 [string processing] 、I/O 等等。下面列出Guava工具包中的常用功能点，以便需要的时候查阅使用。
基本工具 [Basic utilities]
使用和避免null：null是模棱两可的，会引起令人困惑的错误，有些时候它让人很不舒服。很多Guava工具类用快速失败拒绝null值，而不是盲目地接受。
前置条件: 让方法中的条件检查更简单。
常见Object方法: 简化Object方法实现，如hashCode()和toString()。
排序: Guava强大的”流畅风格比较器”
Throwables：简化了异常和错误的传播与检查。
集合[Collections]
Guava对JDK集合的扩展，这是Guava最成熟和为人所知的部分
不可变集合: 用不变的集合进行防御性编程和性能提升。
新集合类型: multisets, multimaps, tables, bidirectional maps等。
强大的集合工具类: 提供java.util.Collections中没有的集合工具。
扩展工具类：让实现和扩展集合类变得更容易，比如创建Collection的装饰器，或实现迭代器。
缓存[Caches]
Guava Cache：本地缓存实现，支持多种缓存过期策略。
函数式风格[Functional idioms]
Guava的函数式支持可以显著简化代码，但请谨慎使用它。
并发[Concurrency]
强大而简单的抽象，让编写正确的并发代码更简单
ListenableFuture：完成后触发回调的Future
Service框架：抽象可开启和关闭的服务，帮助你维护服务的状态逻辑
字符串处理[Strings]
非常有用的字符串工具，包括分割、连接、填充等操作
原生类型[Primitives]
扩展 JDK 未提供的原生类型（如int、char）操作， 包括某些类型的无符号形式
区间[Ranges]
可比较类型的区间API，包括连续和离散类型
I/O
简化I/O尤其是I/O流和文件的操作，针对Java5和6版本
散列[Hash]
提供比Object.hashCode()更复杂的散列实现，并提供布鲁姆过滤器的实现
事件总线[EventBus]
发布-订阅模式的组件通信，但组件不需要显式地注册到其他组件中
数学运算[Math]
优化的、充分测试的数学工具类
反射[Reflection]
Guava 的 Java 反射机制工具类
Spring中的常用工具类
FileCopyUtils；
WebUtil；
