ASM is an all purpose Java bytecode manipulation and analysis framework. It can be used to modify existing classes or dynamically generate classes, directly in binary form. The provided common transformations and analysis algorithms allow easily assembling custom complex transformations and code analysis tools.

The Logging package is a thin bridge between different logging implementations. A library that uses the commons-logging API can be used with any logging implementation at runtime.

Xbean-reflect provides very flexible ways to create objects and graphs of objects for dependency injection frameworks

Commons-compiler contains an API for janino, including the IExpressionEvaluator, IScriptEvaluator, IClassBodyEvaluator and ISimpleCompiler interfaces.

The codec package contains simple encoder and decoders for various formats such as Base64 and Hexadecimal. In addition to these widely used encoders and decoders, the codec package also maintains a collection of phonetic encoding utilities.

This is a part of the Apache Commons Project.

JSON Processing (JSON-P) is a Java API to process (e.g. parse, generate, transform and query) JSON messages. This package contains a reference implementation of that API.

Bnd is a swiss army knife for OSGi, it creates manifest headers based on analyzing the class code, it verifies the project settings, it manages project dependencies, gives diffs jars, and much more.

Although the java.net package provides basic functionality for accessing resources via HTTP, it doesn't provide the full flexibility or functionality needed by many applications. HttpClient seeks to fill this void by providing an efficient, up-to-date, and feature-rich package implementing the client side of the most recent HTTP standards and recommendations.

HttpCore is a set of low level HTTP transport components that can be used to build custom client and server side HTTP services with a minimal footprint. HttpCore supports two I/O models: blocking I/O model based on the classic Java I/O and non-blocking, event driven I/O model based on Java NIO.

This package provides the blocking I/O model library.

OSGi, for Open Services Gateway initiative framework, is a module system and service platform for the Java programming language. This package contains the OSGi org.osgi.service.event module.

Java Compiler Compiler (JavaCC) is the most popular parser generator for use with Java applications. A parser generator is a tool that reads a grammar specification and converts it to a Java program that can recognize matches to the grammar. In addition to the parser generator itself, JavaCC provides other standard capabilities related to parser generation such as tree building (via a tool called JJTree included with JavaCC), actions, debugging, etc.

JMock is a library that supports test-driven development of Java code with mock objects. Mock objects help you design and test the interactions between the objects in your programs.

The jMock library

• makes it quick and easy to define mock objects

• lets you precisely specify the interactions between your objects, reducing the brittleness of your tests

• plugs into your favourite test framework

• is easy to extend.

OSGi, for Open Services Gateway initiative framework, is a module system and service platform for the Java programming language. This package contains the Data Transfer Objects. It is easily serializable having only public fields of primitive types and their wrapper classes, Strings, and DTOs. List, Set, Map and array aggregates may also be used. The aggregates must only hold objects of the listed types or aggregates.

OPS4J stands for Open Participation Software for Java. This package contains utilities and extensions related to resolving properties from different sources.

StringTemplate is a java template engine (with ports for C#, Objective-C, JavaScript, Scala) for generating source code, web pages, emails, or any other formatted text output. StringTemplate is particularly good at code generators, multiple site skins, and internationalization / localization. StringTemplate also powers ANTLR.

PowerMock is a framework that extends other mock libraries such as EasyMock with more powerful capabilities. PowerMock uses a custom classloader and bytecode manipulation to enable mocking of static methods, constructors, final classes and methods, private methods, removal of static initializers and more. By using a custom classloader no changes need to be done to the IDE or continuous integration servers which simplifies adoption.

Pax Exam creates OSGi bundles for testing purposes. It lets the user take control of the OSGi framework, the test framework (e.g. JUnit) and the system under test at the same time.

Joda-Time is a replacement for the Java date and time classes prior to Java SE 8.

Pax Exam creates OSGi bundles for testing purposes. It lets the user take control of the OSGi framework, the test framework (e.g. JUnit) and the system under test at the same time.

Microemulator is a Java 2 Micro Edition (J2ME) CLDC/MIDP Emulator. It demonstrates MIDlet based applications in web browser applet and can be run as a standalone java application.

Hdrhistogram creates histograms that support recording and analyzing sampled data value counts across a configurable integer value range with configurable value precision within the range. Value precision is expressed as the number of significant digits in the value recording, and provides control over value quantization behavior across the value range and the subsequent value resolution at any given level.

Java-jboss-transaction-api-spec implements the Transactions API. A transaction is a unit of work containing one or more operations involving one or more shared resources having ACID (Atomicity, Consistency, Isolation and Durability) properties.

Logback is intended as a successor to the popular log4j project. This module can be assimilated to a significantly improved version of log4j. Moreover, logback-classic natively implements the slf4j API so that you can readily switch back and forth between logback and other logging frameworks such as log4j or java.util.logging (JUL).

Ant is a platform-independent build tool for Java. It is similar to make but is implemented using the Java language, requires the Java platform, and is best suited to building Java projects. Ant uses XML to describe the build process and its dependencies, whereas Make uses Makefile format.