WORK IN PROGRESS
mizdebsk, 25 Oct 2013

==== JVM

Fedora allows multiple Java Virtual Machines (JVMs) to be packaged
independently.  Java packages should not directly depend on any
particulat JVM, but instead require one of three virtual JVM packages
depending of what Java funtionality is required.

*`java-headless`*::

    This package provides a working Java Runtime Environment (JRE)
    with some functionality didabled.  Graphics and audio support may
    be unavailable in this case.  `java-headless` provides
    functionality that is enough for most of packages and avoids
    pulling in a number of graphics and audio libraries as
    dependencies.  Requirement on `java-headless` is appropriate for
    most of Java packages.

*`java`*::

    Includes the same base functionality as `java-headless`, but also
    implements audio and graphics subsystems.  Packages should require
    `java` if they need some functionality from these subsystems, for
    example creating GUI using AWT library.

*`java-devel`*::

    Provides full Java Development Kit (JDK).  In most cases only
    packages related to Java development should have runtime
    dependencies on `java-devel`.  Runtime packages should require
    `java-headless` or `java`.  Some packages not strictly related to
    java development need access to libraries included with JDK, but
    not with JRE (for example `tools.jar`).  That's one of few cases
    where requiring java-devel may be necessary.

Packages that require minimal Java standard version can add versioned
dependencies on one of virtual packages providing Java environment.
For example if packages depending on functionality of JDK 8 can
require `java-headless >= 1:1.8.0`.

.Epoch in versions of JVM packages
[NOTE]
=======
For compatibility with JPackage project packages providing Java 1.6.0
or later use epoch equal to `1`.  This was necessary because package
`java-1.5.0-ibm` from JPackage project had epoch `1` for some reason,
so packages providing other implementations of JVM also had to use
non-zero epoch in order to keep version ordering correct.
=======


TODO

* Java Packages Tools
* Ant
** extra tasks and /etc/ant.d
* Maven
** XMvn
