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Java Configuration Design Update
This page describes a potential update to the Java support code in Gentoo and Funtoo Linux, with the intention of simplifying java-config code and also making it more correct and better integrated with Portage itself. The proposal intends to address deficiencies in the current design of java-utils-2.eclass while maintaining its useful features and avoiding a full rewrite. Rather than replace the current system with more code, the goal is to simplify the existing code while retaining functionality.
Design Challenges
The current Java eclasses have some very interesting and powerful features, yet are lacking in some areas.
Dependency Handling
Currently, java-utils-2.eclass uses depend-java-query to automatically select the most optimal Java VM for building. This is a sophisticated feature that is intended to be 'smart', yet it has some flaws. These flaws are fixable:
- While JVM auto-selection is smart, it is not always correct -- it doesn't use Portage's API, but instead uses regexes to parse the currently-executing ebuild's DEPEND string. Ideally, Portage API would be used to always generate a completely correct result.
- Related to the regex issue, the code in depend-java-query is complex as it tries to duplicate some functionality that could be handled better by Portage's API.
Atoms
Currently, eselect java-vm and java-config have their own "atoms" that they use to identify Java virtual machines, which seems to be ${PN}-${SLOT}. But why create a new kind of atom? Portage already has atoms, and we should try to use them if they work for us. So this proposal will also attempt to "merge in" support for Portage-style naming of Java VMs.
Proposal
java-config Settings
This proposal involves a minor upgrade to the java-config settings for a JVM -- adding a PORTAGE_ATOM setting to the file, which allows the java-config atom to be linked to the Portage atom:
/usr/share/java-config-2/vm/oracle-jdk-bin-1.7 (bash source code) - Java-config settings# Copyright 1999-2011 Gentoo Foundation
# Distributed under the terms of the GNU General Public License v2
# $Header: /var/cvsroot/gentoo-x86/dev-java/oracle-jdk-bin/files/oracle-jdk-bin-1.7.env,v 1.2 2011/11/17 22:49:56 caster Exp $
VERSION="Oracle JDK 1.7.0.60"
JAVA_HOME="/opt/oracle-jdk-bin-1.7.0.60"
JDK_HOME="/opt/oracle-jdk-bin-1.7.0.60"
JAVAC=${JAVA_HOME}/bin/javac
PATH="${JAVA_HOME}/bin:${JAVA_HOME}/jre/bin"
ROOTPATH="${JAVA_HOME}/bin:${JAVA_HOME}/jre/bin"
LDPATH="${JAVA_HOME}/jre/lib/amd64/:${JAVA_HOME}/jre/lib/amd64/xawt/:${JAVA_HOME}/jre/lib/amd64/server/"
MANPATH="/opt/oracle-jdk-bin-1.7.0.60/man"
PROVIDES_TYPE="JDK JRE"
PROVIDES_VERSION="1.7"
BOOTCLASSPATH="${JAVA_HOME}/jre/lib/resources.jar:${JAVA_HOME}/jre/lib/rt.jar:${JAVA_HOME}/jre/lib/sunrsasign.jar:${JAVA_HOME}/jre/lib/jsse.jar:${JAVA_HOME}/jre/lib/jce.jar:${JAVA_HOME}/jre/lib/charsets.jar:${JAVA_HOME}/jre/classes"
GENERATION="2"
ENV_VARS="JAVA_HOME JDK_HOME JAVAC PATH ROOTPATH LDPATH MANPATH"
VMHANDLE="oracle-jdk-bin-1.7"
BUILD_ONLY="FALSE"
PORTAGE_ATOM="dev-lang/oracle-jdk-bin-1.7.0.60"
With this very minor and easy-to-implement change, new possibilities are available -- namely, for java-config code to tap into the Portage API and leverage its advanced dependency handling functionality.
Provides
This section is not a requirement for the implementation of this proposal, but a suggestion for future Portage development.
Currently, the functionality that is provided by each JVM is stored in the java-config file shown above, namely in the PROVIDES_TYPE and PROVIDES_VERSION variables. This works for us, though it is unfortunate that the (in my opinion) not completely thought-out GLEP 37 was implemented, which deprecated the PROVIDES variable in Portage. This is a useful variable because it gave us a "link" from the installed package to the virtual it provided. No such link currently exists, which is a reduction in useful functionality.
It is suggested that PROVIDES is un-deprecated, and used by ebuilds solely for recording what virtuals are provided by the ebuild, so that they can be queried later once the package is installed. This would allow PROVIDES_TYPE and PROVIDES_VERSION -- functionality duplicated by the Java tools -- to be removed, further reducing the complexity of the Java tools codebase.