Proper Versus Sandbox

The maintainers of the Commons project divide contributed code into two main areas, a "proper" suite and a "sandbox." The proper code is considered stable (and popular) enough to warrant a certain level of commitmentthe interfaces are expected not to change without warning, and the code is considered to have been tested well enough for production use. The sandbox, on the other hand, is open to anyone already accepted as a committer on another Jakarta project.

The bulk of this book is devoted to the most popular and useful of the proper componentsfor more information on the sandbox components, see Chapter 14, "Other Projects."

The proper components from the Commons package identified in Table 1-1 are covered in this book.

Table 1-1. Covered Proper Components

BeanUtils	Chapter 7	Easy-to-use wrappers around the Java reflection and introspection APIs.
CLI (Command Line Interface)	Chapter 13	Provides a simple API for working with command line arguments, options, option groups, mandatory options, and default help output.
Codec	Chapter 12	Contains phonetic encoders, Hex, Base64, and a URL encoder.
Collections	Chapter 11	Extends and augments the Java Collections Framework.
DBCP	Chapter 6	Database connection pooling services. Based on the Pool component, described in Chapter 5, "Pool."
FileUpload	Chapter 2	Adds robust, high-performance, file upload capability to servlets and web applications.
HttpClient	Chapter 3	A framework for working with the client side of the HTTP protocol.
JXPath	Chapter 8	Utilities for manipulating Java classes that conform to the JavaBeans naming conventions using the XPath syntax. It also supports maps, DOM, and other object models.
Lang	Chapter 10	A very common set of utility classes, including routines for escaping text, enums, math, and time.
Logging	Chapter 9	A wrapper around a variety of logging API implementations (including log4j and JDK logging).
Net	Chapter 4	A collection of network utilities including Telnet, FTP, and NNTP clients.
Pool	Chapter 5	A generic object pooling interface, with classes for creating object pools and several general purpose pool implementations.

The proper projects listed in Table 1-2 are not covered by this book. Some of these projects merely provide implementations of certain standards (e.g., the JSP Expression Language), are handled by other frameworks (e.g., DbUtils), or are too narrowly focused for coverage in this text.

Table 1-2. Additional Proper Components

Betwixt	Services for mapping JavaBeans to XML documents, and vice versa.
Chain	Provides a "Chain of Responsibility" pattern implementation for organizing complex processing flows.
Configuration	Tools to assist in the reading of configuration/preferences files in various formats.
Daemon	An alternative invocation mechanism for Unix-daemon-like Java code.
DbUtils	JDBC helper library that factors out mundane resource cleanup code for common database tasks.
Digester	An XML-to-Java-object mapping utility commonly used for parsing XML configuration files.
Discovery	Provides tools for locating resources (including classes) by mapping service/reference names to resource names using a variety of schemes.
EL	An interpreter for the Expression Language defined by the JavaServer Pages (TM) specification, version 2.0.
IO	Collection of I/O utilities.
Jelly	XML-based scripting and processing engine.
Jexl	An expression language that extends the Expression Language of the JSTL.
Latka	An HTTP functional testing suite for automated QA, acceptance, and regression testing.
Launcher	Cross-platform Java application launcher. Eliminates the need for a batch or shell script to launch a Java application.
Math	Library of lightweight, self-contained mathematics and statistics components addressing the common practical problems not immediately available in the Java programming language.
Modeler	Provides mechanisms to create Model MBeans compatible with the Java Management Extensions (JMX) specification.
Primitives	Smaller, faster, and easier-to-work-with types supporting Java primitive types, with an emphasis on collections.
Validator	Simple, extendable framework to define validation methods and validation rules in an XML file. Supports internationalization of rules and error messages.