Additional Commons Proper Projects

The Commons proper projects not described in detail in this book are described in a bit more detail in the following. For more information on these packages, visit the http://jakarta.apache.org/commons/ web site.

Betwixt

Services for mapping JavaBeans to XML documents, and vice versa. Intended for use when a JavaBean wants to be serialized to XML. Note that JDK 1.4 introduced long-term serialization-to-XML capability (http://java.sun.com/j2se/1.4.2/docs/guide/beans/changes14.html).

Chain

Provides a "Chain of Responsibility" pattern implementation for organizing complex processing flows. As of this writing, despite the status as a proper package (not sandbox), there have been no official releases.

Configuration

Tools to assist in the reading of configuration/preferences files in various formats. Allows for configuration information from Properties files, XML documents, JNDI, and JDBC data sources to be accessed in a unified manner.

Daemon

An alternative invocation mechanism for UNIX-daemon-like Java code. Specifically, this project contains native code for receiving system status notifications from the operating system for both UNIX and Windows. If you are writing server code and are interested in this project, you may also be interested in the JDesktop Integration Components (JDIC), https://jdic.dev.java.net/.

DbUtils

JDBC helper library that factors out mundane resource cleanup code for common database tasks. DbUtils is intended to remove the drudgery of raw JDBC, but it is not an object/relational database package. It is simply a helper library.

Digester

An XML-to-Java-object mapping utility commonly used for parsing XML configuration files. Intended to serve as a common framework for dealing with large configuration files; for many application developers, starting with a generic XML library (such as JDOM, http://www.jdom.org/) may be more appropriate.

Discovery

Provides tools for locating resources (including classes) by mapping service/reference names to resource names using a variety of schemes. It is only at a 0.2 release.

EL

An interpreter for the Expression Language defined by the JavaServer Pages™ specification, version 2.0. This might be useful as a scripting language to be embedded in certain applications.

IO

Collection of I/O utilities, including stream implementations, file filters, and endian classes. The org.apache.commons.io.CopyUtils class contains a comprehensive set of static methods for copying from a String, byte[], InputStream, or Reader to an OutputStream or Writer. Similarly, the org.apache.commons.io.IOUtils class contains additional tools for safely closing streams and creating String and byte arrays from streams and readers. The org.apache. commons.io.FileUtils class contains methods for retrieving different components of a file path (directory name, file base name, file extension), methods for copying files to other files and directories, and methods for querying, deleting, and cleaning directories. Additional classes provide filters for use with FileDialog, or for converting the endian ordering of bytes.

Jelly

XML-based scripting and processing engine. While Jelly has found some success in projects such as Maven, the general consensus is that XML is a poor choice for a programming languageeven the creator of Jelly apologized at http://radio.weblogs.com/0112098/2004/03/26.html#a472.

Jexl

An expression language that extends the Expression Language of the JSTL. Note that this package is not compatible with JSTL or JSPit is a nonstandard expression language.

Latka

An HTTP functional testing suite for automated QA, acceptance, and regression testing. XML is used to define HTTP(S) requests and validation tests.

Launcher

Cross-platform Java application launcher. Eliminates the need for a batch or shell script to launch a Java class. Originally developed for Tomcat, it allows for complex configurations of class path and system properties.

Math

Library of lightweight, self-contained mathematics and statistics components addressing the common practical problems not immediately available in the Java programming language. This includes basic statistics and linear equation support.

Modeler

Provides mechanisms to create Model MBeans compatible with the Java Management Extensions (JMX) specification. If you wish to expose management of your application via JMX, you will likely want to investigate this package.

Primitives

Smaller, faster, and easier to work with types supporting Java primitive types, with an emphasis on collections. The provided collection of types and utilities is optimized for working with Java primitives (boolean, byte, char, double, float, int, long, short).

Validator

Simple, extendable framework to define validation methods and validation rules in an XML file. Supports internationalization of rules and error messages. Includes basic validation rules for credit card numbers, dates, email addresses, and URLs.