Proposal for clazz Package

(0) Rationale

The Java Reflection Framework provides a set of classes for accessing and calling classes, methods and fields dynamically at runtime. In addition, the beans Introspector class provides for examination of java beans. Together these offer very useful functionality that is widely used by todays applications.

There is a need for reflection and introspection code in a great many of the Commons, Jakarta and Apache projects. However, the standard Java classes have proved inadequate, causing each project to write their own reflection helper classes. In addition, many projects also require metadata to be stored against classes and properties. This is not supported by the current Java APIs.

The Clazz package will focus on introspection and class manipulation. Reflection helper code is located in the [lang] package.

(1) Scope of the Package

The Clazz package shall create and maintain a package that provides introspection and class manipulation handling built upon the Java Reflection Framework and other providers, such as byte and source code readers/generators.

The package should:

handle all classes, not just beans
support extensible metadata (not just for GUI builders)
handle normal (today) bean conventions (get/set/add/put methods)
handle future conventions that are not yet standard
support method overloading
provide a complete alternative to using java.beans.Introspector
be simple to learn

In terms of code, [clazz] would begin by having classes/interfaces that represent a class, method and field like reflection. It would then provide mechanisms to build the structure via reflection and BCEL, and ideally to generate classes from the structure using BCEL. Note: One possibility would be to say that the BCEL dependency belongs in BCEL, and the commons version just uses reflection. [clazz] would also provide mechanisms for identifying methods as being property methods, coping with modern conventions such as addXxx(), lists and maps that the beans introspector doesn't. This would allow [clazz] to be used by betwixt and digester to add flexibility. (I remember reading a case where some swedish company had insisted on localising the words get and set in bean methods - [clazz] could cope with that)

(1.5) Interaction With Other Packages

clazz relies only on standard JDK 1.2 (or later) APIs for production deployment. It utilizes the JUnit unit testing framework for developing and executing unit tests, but this is of interest only to developers of the component.

No external configuration files are utilized.

(2) Initial Source of the Package

These types of classes are splashed around various Apache subprojects. We intend to seek them out and integrate them.

The proposed package name for the new component is org.apache.commons.clazz.

(3) Required Jakarta-Commons Resources

SVN repository - New directory clazz in the jakarta-commons SVN repository.
Mailing List - Discussions will take place on the general dev@commons.apache.org mailing list. To help list subscribers identify messages of interest, it is suggested that the message subject of messages about this component be prefixed with [clazz].
Bugzilla - New component "clazz" under the "Commons" product category, with appropriate version identifiers as needed.
Jyve FAQ - New category "commons-clazz" (when available).

(4) Initial Committers

The initial committers on the Clazz component shall be: