F40 Change Proposal: Java 21 (System-Wide)

java-21-openjdk as the system JDK in F40


This is a proposed Change for Fedora Linux.
This document represents a proposed Change. As part of the Changes process, proposals are publicly announced in order to receive community feedback. This proposal will only be implemented if approved by the Fedora Engineering Steering Committee.

:link: Summary

Update the system JDK in Fedora from java-17-openjdk to java-21-openjdk.

:link: Owner

:link: Expected schedule

  • During January 2024, we will create a new package, java-21-openjdk, which will be a clone of java-latest-openjdk, which contains STS versions of OpenJDK (currently 21) and will move to JDK 22 in February/March.
  • December 2023 I will do mass rebuild in copr
    • all maintainers will be informed about the results
  • January 2023 I will do second mass rebuild in copr
    • all maintainers will be informed about the results
  • February 2023 mass rebuild in rawhide - side tag
    • FTBFS bugs will be filed
  • February 2023 the sidetag will be merged
  • Change Checkpoint: 100% Code Complete Deadline TBD
    • hard deadline for feature completed

:link: Detailed Description

Fedora currently ships:

  • java-1.8.0-openjdk (LTS)
  • java-11-openjdk (LTS)
  • java-17-openjdk (LTS), system JDK
  • java-latest-openjdk (currently JDK21)
  • java-21-openjdk will be cloned from java-latest-openjdk

Therefore, every package honoring the packaging rules and requiring java via java-headless or java-devel is built in koji using java-17-openjdk-devel and pulling java-17-openjdk during runtime (see java ). Also, javapackaging-tools are using java-11-openjdk as hardcoded runtime (see changes).

We were intentionally delaying jdk11 on-boarding for stability reasons. But there is reason for this approach with 21 (for recall, see Changes/Java11 - Fedora Project Wiki)

Major incompatibility is again (as we were bumping 8->11) encapsulation. What was hidden is now even more hidden and few more parts were hidden. Luckily, most of the projects, when shifted to 11, did it properly. Still few projects may hit usage of some newly restricted APIs.

:link: Feedback

:link: Benefit to Fedora

JDK21 was released a while ago, but compatibility with JDK 17 is good enough and it is a stable release. Although we can expect some group of packages to use jdk8 forever, and some other (much smaller) group of packages stay on jdk11 for a while, the java stack should be able to use the JDK 21. Both JDK 8 and JDK 11 will remain part of Fedora as long as they are supported upstream, and there is a target audience in our OS.

:link: Scope

:link:) To keep the java-17-openjdk (and lower versions of JDK), but to remove its java/javac versionless provides, make java-21-openjdk the provider of java, javac and other versionless provides, and keep java-latest-openjdk as rolling package for STS JDKs)

  • will guarantee fedora to be pure JDK21 distro.
  • will allow maintainers of JDK21 (or higher) incompatible packages to keep using JDK 17, JDK 11 and JDK 8
    • if any package depends on a package built by JDK 21, JDK 17, JDK 11 and JDK 8 may not be able to pick up that dependency.
    • this may lead to quite a lot of bundling or compat packages, but that may be acceptable
    • people developing JDK8 and JDK11 applications will very likely stay with fedora
    • we are bumping the system JDK every time a new JDK LTS comes up and it proved itself as a good practice

While quite a lot of users will rejoice, there may be cases where application is very hard to migrate to JDK11, so the contingency plan should be taken very serious.

:link: Bytecode version

:link: Workflow

:link: Change owners

  • Feature will be implemented in side tag
    • –target f40-java21 is tag of choice
    • In its mass rebuild, approximately XYZ packages were built, and ABC failed. FTBFS bugs filled, most of them needs manual fix later
  • the JDK 17 and JDK 21 packages will be changed for this side tag
  • the mass rebuild of java stack will start
    • if necessary, several rounds of them
  • Failures will be gathered by me and few other volunteers
    • Most common issues and theirs fixes will be published
    • Package maintainers will be notified in case of failure via bugzilla
  • Depending on the fail rate, importance of failed packages and effort to fix them
    • the side tag will be merged to Fedora
    • or the contingency plan will be activated

:link: Other developers

  • should fix their packages
    • this usually means to update to newer version, which supports jdk21
  • or to retire them if they appear non-fixable
  • or to base them on JDK11 without much warranty (as they will need to compat most of dependency chain)

:link: Other

  • Proposal owners:

    • based on above, adapt jdk11 and jdk17 package provides
    • If necessary tune the build environment
  • Other developers:

    • based on selected approach to tune the main build tools
      • jpackage-tools and maven will affected
    • based on selected approach to tune the rpmbuild/macros
    • many java package maintainers will maybe need to adapt theirs packages
      • FTBFS bugs connected with this proposal, maybe with pagure ticket to allow discussion.
      • Solutions to most common errors should be gathered and published
  • Release engineering: TICKET_TBD (a check of an impact with Release Engineering is needed)

    • mass rebuild will be required for this change
  • Policies and guidelines: how to deal with build failures, eventually how to use some jdk17 specific build features will be provided

  • Trademark approval: N/A (not needed for this Change)

:link: Upgrade/compatibility impact

Once the change is implemented properly, the update should be flawless and seamless

:link: How To Test

  • only JDK 21 should remain the only system JDK after installing base javastack on clean system
  • the JDK 8, JDK 11, JDK 17, JDK 21 and java-latest-openjd can co-exist on one system
  • JDK 21 will be selected by default and will run most of the base java stack

:link: User Experience

  • Standard user should be still be able to use java stack without even noticing the change.
  • Standard developer should still be able develop any java application comfortably
  • Standard packager will not suffer to much, and should be able to pack any java application for fedora

:link: Dependencies

Around 2000 packages will need attendance

$ repoquery -q --whatrequires java-headless |wc -l 736 $ repoquery -q --whatrequires java | wc -l 41 $ repoquery -q --whatrequires java-devel | wc -l 13 $ repoquery -q --whatrequires java-1.8.0-openjdk-headless |wc -l 653 $ repoquery -q --whatrequires java-1.8.0-openjdk | wc -l 8 $ repoquery -q --whatrequires java-1.8.0-openjdk-devel | wc -l 4 $ repoquery -q --whatrequires java-11-openjdk-headless |wc -l 663 $ repoquery -q --whatrequires java-11-openjdk | wc -l 8 $ repoquery -q --whatrequires java-11-openjdk-devel | wc -l 5 $ repoquery -q --whatrequires java-17-openjdk-headless |wc -l 757 $ repoquery -q --whatrequires java-17-openjdk |wc -l 55 $ repoquery -q --whatrequires java-17-openjdk-devel |wc -l 20

with src repos on, build time depndnecies:

set +x ;echo “dont forget to enable all (correct fedora, fedotra-testing, fedora modules) SOURCE repos (sections in .repo files)!” ; for x in ant maven-local maven mvn xmvn java-headless java java-devel java-1.8.0-openjdk-headless java-1.8.0-openjdk java-1.8.0-openjdk-devel java-11-openjdk-headless java-11-openjdk java-11-openjdk-devel ; do for y in “” “–arch src” ;do set -x ; repoquery $y -q --whatrequires $x |wc -l ; set +x ; done; done dont forget to enable all (correct fedora, fedotra-testing, fedora modules) SOURCE repos (sections in .repo files) + repoquery --arch src -q --whatrequires ant 152 + repoquery --arch src -q --whatrequires maven-local 401 + repoquery --arch src -q --whatrequires maven 4 + repoquery --arch src -q --whatrequires mvn 0 + repoquery --arch src -q --whatrequires xmvn 0 + repoquery --arch src -q --whatrequires java-headless 5 + repoquery --arch src -q --whatrequires java 0 + repoquery --arch src -q --whatrequires java-devel 207 + repoquery --arch src -q --whatrequires java-1.8.0-openjdk-headless 6 + repoquery --arch src -q --whatrequires java-1.8.0-openjdk 0 + repoquery --arch src -q --whatrequires java-1.8.0-openjdk-devel 19 + repoquery --arch src -q --whatrequires java-11-openjdk-headless 0 + repoquery --arch src -q --whatrequires java-11-openjdk 0 + repoquery --arch src -q --whatrequires java-11-openjdk-devel 15

Packages needing major work will be

  • java-17-openjdk
  • java-21-openjdk
  • javapackages-tools
  • maybe maven base

:link: Contingency Plan

  • If the mass rebuild, after the changes are applied, breaks too many packages, or some crucial component will be unfixable, JDK 17 must be restored back to the position of system JDK.
  • Contingency mechanism: Return jdk8 as system jdk and mass rebuild again. Note, that this may be very hard, because during build of packages by jdk8, by jdk11 built dependencies will be picekd up, so build will fail. Maybe several iterations of mass rebuild will be needed.
  • Contingency deadline: Announce release blocking deliverables Tue 2022-02-01 Tue 2022-02-01 0 (8days before branching, 22 before beta freeze)
  • Blocks release? Yes
  • Blocks product? N/A
  • In general, going back will be, in my opinion, impossible. Once the decision is taken, java stack should be fixed, and where it can not be fixed, it has to migrate to compat packages, or bundled-dependencies packages, or be orphaned.

:link: side tag


  • for these changes, Fedora has technology known as side tag
  • I do not have experience with it, but it is making the contingency plan much smoother
  • it is an approach, which will be used first

:link: Documentation

:link: common issues packagers can face and gathered solutions

Contacts: ask on devel@lists.fedoraproject.org or java-devel@lists.fedoraproject.org or directly to me pmikova@redhat.com Threads of “F40 system wide change, java-21-openjdk as a system JDK”

Major database can be browsing of closed bugs of blockers of Invalid Bug ID ; unluckily, when it was analysed, it was not summarised up (that would actually double the work)

:link: My package can not work with JDK 21

No program can say, that it does not support JDK 21, because any javac/java application can be remade to work with JDK 21 - see https://jvanek.fedorapeople.org/devconf/2017/portingjavaInternalToJdk9/portingOfItwToJdk9-II.pdf (really all except package split over modules, which is impossible)

Now above mentioned approaches are indeed hacked, and I discourage everybody to do so. The upstream should be moved to jdk21, and not much excuses are around to support to not to do so. If you package is really bound to JDK 17, you can move to the version-full requires:

BuildRequires: java-17-openjdk(-devel)


Requires: java-17-openjdk(-headless).

In addition, if you work with maven/ant or similar builders, you must set export JAVA_HOME=/usr/lib/jvm/java-11-openjdk before calling it. javapackage-tools and comp are made to accept it.

However there is a trap - the packages you are depending on. Once some of your dependencies will be compiled with --target > 8, you are doomed, and you have to bundle it or create its compat version. By doing so you can easily end up in dependency hell.

Please, try to avoid this as much as possible!

:link: Intermediate step build with java-17-openjdk-devel and run with java (that means any sytem java, eg java-21-openjdk)

Some projects support JDK21 for runtime, but not for compile time.

Buildrequires: java-17-openjdk-devel … Requires: java(-headless) … %build … export JAVA_HOME=/usr/lib/jvm/java-17-openjdk …

Should work for a while. See the “My package can not work with jdk11” section

:link: My package is not in your copr!

If your package is not listed in the copr rebuild repo, I can see two causes

  • You have very indirect BR on java.
    • Solution
    • Email me (pmikova@redhat.com) or ping me (pmikova), I will gladly add you package(s)
  • You have exact requires on java-11-openjdk(-devel)
    • Solution
    • Unless you have good reason, you are actually breaking packaging guidelines. Switch to java-devel. Once done, again let me know and I will gladly add your package
    • If you can’t, then you most likely can not bump to jdk17, and you will live with jdk11 until it dies,

:link: Wrong source/target version


[ERROR] Source option 1.3 is no longer supported. Use 7 or later. [ERROR] Target option 1.3 is no longer supported. Use 1.7 or later.


-do-compile: [mkdir] Created dir: /builddir/build/BUILD/jpanoramamaker-5/build/empty [javac] Compiling 45 source files to /builddir/build/BUILD/jpanoramamaker-5/build/classes [javac] warning: [options] bootstrap class path not set in conjunction with -source 5 [javac] error: Source option 5 is no longer supported. Use 7 or later. [javac] error: Target option 1.5 is no longer supported. Use 1.7 or later. BUILD FAILED

:link: Release Notes