Are there any experiences and recommendations regarding openHAB 5 and java 25 (Temurin)?

wurkel · October 22, 2025, 1:25pm

I am with Ubuntu 24.04.3 LTS (noble).

mstormi · October 22, 2025, 5:34pm

Not that I’ve heard of any.
So please contribute yourself: deploy it on your system and let us know. Thanks.

wurkel · October 23, 2025, 5:37am

You’re absolutely right, I can test that myself, but I thought there was already some information available that I hadn’t found in my research.

Here are my findings:
In a nutshell: openHAB 5.0.2 (release build) does not start with Java 25.

The details:
Here is the status after starting with
$ java --version
openjdk 25 2025-09-16 LTS
OpenJDK Runtime Environment Temurin-25+36 (build 25+36-LTS)
OpenJDK 64-Bit Server VM Temurin-25+36 (build 25+36-LTS, mixed mode, sharing)

$ sudo systemctl status openhab
● openhab.service - openHAB - empowering the smart home
Loaded: loaded (/usr/lib/systemd/system/openhab.service; enabled; preset: enabled)
Active: activating (auto-restart) (Result: exit-code) since Thu 2025-10-23 06:26:56 CEST; 3s ago
Docs: Introduction | openHAB
https://community.openhab.org
Process: 590007 ExecStart=/usr/share/openhab/runtime/bin/karaf ${OPENHAB_STARTMODE} (code=exited, status=1/FAILURE)
Main PID: 590007 (code=exited, status=1/FAILURE)
CPU: 758ms

Oct 23 06:26:56 ubuntu24-qnap systemd[1]: openhab.service: Service will restart (restart setting)
Oct 23 06:26:56 ubuntu24-qnap systemd[1]: openhab.service: Changed running → failed-before-auto-restart
Oct 23 06:26:56 ubuntu24-qnap systemd[1]: openhab.service: Unit entered failed state.
Oct 23 06:26:56 ubuntu24-qnap systemd[1]: openhab.service: Consumed 758ms CPU time.
Oct 23 06:26:56 ubuntu24-qnap systemd[1]: openhab.service: Next restart interval calculated as: 5s
Oct 23 06:26:56 ubuntu24-qnap systemd[1]: openhab.service: Changed failed-before-auto-restart → auto-restart
Oct 23 06:26:56 ubuntu24-qnap systemd[1]: openhab.service: Control group is empty.
Oct 23 06:27:01 ubuntu24-qnap systemd[1]: openhab.service: Service restart interval 5s expired, scheduling restart.
Oct 23 06:27:01 ubuntu24-qnap systemd[1]: openhab.service: Trying to enqueue job openhab.service/start/restart-dependencies
Oct 23 06:27:01 ubuntu24-qnap systemd[1]: openhab.service: Installed new job openhab.service/start as 28854
Oct 23 06:27:01 ubuntu24-qnap systemd[1]: openhab.service: Enqueued job openhab.service/start as 28854
Oct 23 06:27:01 ubuntu24-qnap systemd[1]: openhab.service: Scheduled restart job, restart counter is at 39.
Oct 23 06:27:01 ubuntu24-qnap systemd[1]: openhab.service: Changed auto-restart → auto-restart-queued
Oct 23 06:27:01 ubuntu24-qnap systemd[1]: openhab.service: Will spawn child (service_enter_start): /usr/share/openhab/runtime/bin/karaf
Oct 23 06:27:01 ubuntu24-qnap systemd[1]: openhab.service: Passing 0 fds to service
Oct 23 06:27:01 ubuntu24-qnap systemd[1]: openhab.service: About to execute: /usr/share/openhab/runtime/bin/karaf “${OPENHAB_STARTMODE}”
Oct 23 06:27:01 ubuntu24-qnap systemd[1]: openhab.service: Forked /usr/share/openhab/runtime/bin/karaf as 590118
Oct 23 06:27:01 ubuntu24-qnap systemd[1]: openhab.service: Changed auto-restart-queued → running
Oct 23 06:27:01 ubuntu24-qnap systemd[1]: openhab.service: Job 28854 openhab.service/start finished, result=done
Oct 23 06:27:01 ubuntu24-qnap systemd[1]: Started openhab.service - openHAB - empowering the smart home.
Oct 23 06:27:01 ubuntu24-qnap (karaf)[590118]: Found cgroup2 on /sys/fs/cgroup/, full unified hierarchy
Oct 23 06:27:01 ubuntu24-qnap systemd[1]: openhab.service: User lookup succeeded: uid=130 gid=137
Oct 23 06:27:01 ubuntu24-qnap (karaf)[590118]: Found cgroup2 on /sys/fs/cgroup/, full unified hierarchy
Oct 23 06:27:01 ubuntu24-qnap systemd[1]: openhab.service: Child 590121 belongs to openhab.service.

I looked at /lib/systemd/system/openhab.service and started the service manually:

$ /usr/share/openhab/runtime/bin/karaf daemon
JVM must be version 21. JVM version 25 is unsupported (JAVA_HOME=/usr/lib/jvm/temurin-25-jdk-amd64)

I changed the check from 21 to 25 in /usr/share/openhab/runtime/bin/karaf :

# Determine the JVM version and check that it is version 21
checkJvmVersion
if [ “${VERSION}” -ne “21” ]; then
    die “JVM must be version 21. JVM version ${VERSION} is unsupported (JAVA_HOME=$JAVA_HOME)”
fi

The status changed:

$ sudo systemctl status openhab
● openhab.service - openHAB - empowering the smart home
Loaded: loaded (/usr/lib/systemd/system/openhab.service; enabled; preset: enabled)
Active: active (running) since Thu 2025-10-23 06:50:29 CEST; 18s ago
Docs: Introduction | openHAB
https://community.openhab.org
Main PID: 607862 (java)
Tasks: 19 (limit: 4605)
Memory: 149.1M (peak: 149.4M)
CPU: 16.073s
CGroup: /system.slice/openhab.service
└─607862 /usr/bin/java -XX:-UsePerfData -Dopenhab.home=/usr/share/openhab -Dopenhab.conf=/etc/openhab -Dopenhab.runtime=/usr/share/openhab/runtime -Dopenhab. userdata=/var/lib/openhab -Dopenhab.logdir=/var/log/openhab -Dfelix.cm.dir=/var/lib/op>

Oct 23 06:50:29 ubuntu24-qnap systemd[1]: openhab.service: Job 41453 openhab.service/start finished, result=done
Oct 23 06:50:29 ubuntu24-qnap systemd[1]: Started openhab.service - openHAB - empowering the smart home.
Oct 23 06:50:29 ubuntu24-qnap (karaf)[607862]: Found cgroup2 on /sys/fs/cgroup/, full unified hierarchy
Oct 23 06:50:29 ubuntu24-qnap systemd[1]: openhab.service: User lookup succeeded: uid=130 gid=137
Oct 23 06:50:29 ubuntu24-qnap (karaf)[607862]: Found cgroup2 on /sys/fs/cgroup/, full unified hierarchy
Oct 23 06:50:29 ubuntu24-qnap systemd[1]: openhab.service: Child 607865 belongs to openhab.service.
Oct 23 06:50:36 ubuntu24-qnap karaf[607862]: WARNING: A terminally deprecated method in sun.misc.Unsafe has been called
Oct 23 06:50:36 ubuntu24-qnap karaf[607862]: WARNING: sun.misc.Unsafe::staticFieldOffset has been called by org.eclipse.osgi.internal.url.MultiplexingFactory (file:/usr/share/openhab/runtime/system/org/eclipse/platform/org.eclipse.osgi/3.18.0/org.eclipse.o>
Oct 23 06:50:36 ubuntu24-qnap karaf[607862]: WARNING: Please consider reporting this to the maintainers of class org.eclipse.osgi.internal.url.MultiplexingFactory
Oct 23 06:50:36 ubuntu24-qnap karaf[607862]: WARNING: sun.misc.Unsafe::staticFieldOffset will be removed in a future release

In /var/log/openhab/openhab.log , I actually only saw exceptions like the following:

2025-10-23 06:51:08.828 [ERROR] [org.apache.felix.configadmin ] - [org.osgi.service.cm.ManagedService, id=34, bundle=5/mvn:org.ops4j.pax.logging/pax-logging-log4j2/2.2.8]: Unexpected problem updating configuration org.ops4j.pax.logging
java.lang.UnsupportedOperationException: getSubject is not supported
at javax.security.auth.Subject.getSubject(Subject.java:277) ~[?:?]
at org.apache.felix.eventadmin.impl.handler.EventAdminImpl.prepareEvent(EventAdminImpl.java:146) ~[?:?]
at org.apache.felix.eventadmin.impl.handler.EventAdminImpl.postEvent(EventAdminImpl.java:180) ~[?:?]
at org.apache.felix.eventadmin.impl.security.EventAdminSecurityDecorator.postEvent(EventAdminSecurityDecorator.java:79) ~[?:?]
at org.ops4j.pax.logging.spi.support.EventAdminConfigurationNotifier.configurationDone(EventAdminConfigurationNotifier.java:49) ~[bundleFile:?]
at org.ops4j.pax.logging.log4j2.internal. PaxLoggingServiceImpl.configureLog4J2(PaxLoggingServiceImpl.java:596) ~[bundleFile:?]
at org.ops4j.pax.logging.log4j2.internal.PaxLoggingServiceImpl.updated(PaxLoggingServiceImpl.java:342) ~[bundleFile:?]
at org.ops4j.pax.logging.log4j2.internal.LoggingManagedService.updated(LoggingManagedService.java:37) ~[bundleFile:?]
at org.apache.felix.cm.impl.helper.ManagedServiceTracker.updated(ManagedServiceTracker.java:189) ~[bundleFile:?]
at org.apache.felix.cm.impl.helper.ManagedServiceTracker.updateService(ManagedServiceTracker.java:152) [bundleFile:?]
at org.apache.felix.cm.impl.helper.ManagedServiceTracker.provideConfiguration(ManagedServiceTracker.java:85) [bundleFile:?]
at org.apache.felix.cm.impl.ConfigurationManager$ManagedServiceUpdate.provide(ConfigurationManager.java:1131) [bundleFile:?]
at org.apache.felix.cm.impl.ConfigurationManager$ManagedServiceUpdate.run(ConfigurationManager.java:1087) [bundleFile:?]
at org.apache.felix.cm.impl.UpdateThread.run0(UpdateThread.java:122) [bundleFile:?]
at org.apache.felix.cm.impl.UpdateThread.run(UpdateThread.java:84) [bundleFile:?]
at java.lang.Thread.run(Thread.java:1474) [?:?]

It seems that the Apache components used are not prepared for Java 25.
I have stopped the experiment.

hmerk · October 23, 2025, 7:36am

You can check progress here

github.com/openhab/openhab-core

Java 25 Support

opened 06:35PM - 14 Sep 25 UTC

holgerfriedrich

infrastructure

This issues is to summarise the current state of Java 25 support. Java 25 is the… next LTS release and is likely to be supported by OH in the future. Java 25 brings a lot of improvements. I am curious especially about [JEP 483: Ahead-of-Time Class Loading & Linking](https://openjdk.org/jeps/483)! How much faster will be the start on a RPi? The migration will be done slowly. We will use Java 21 as the major and supported Java version. In the background, we will work hard to remove blockers. I will add a Java 25 build to the CI, first only compiling with Java 25 compiler configured to generate Java 21 code. This will be extended over the next months once we are able to remove blockers. Those are the steps to be taken: ### Compile with Java 25, generate Java 21 bytecode - [x] Compile - [x] Unit-tests - [ ] iTests - work with bndtools 7.2 and junit downgraded below v13 (due to transitive dependency) - [x] Code Analysis - [ ] Blocker: bndtools 7.1 -> wait for 7.2 release - [ ] Blocker: bndtools 7.2-SNAPSHOT require junit to be downgraded below v13, see bndtools/bnd#6651 for an explanation why this is the case.... :-( - [ ] WIP: https://github.com/openhab/openhab-core/pull/5021 ### Compile with Java 25, generate (mostly) Java 25 bytecode - [ ] tools like ~~maven-shade-plugin~~, ecj are not supporting Java 25 bytecode -> limit this bundles to Java 24 - [ ] Code Analysis - tools to not yet support Java 25 bytecode -> do the necessary upgrades, release static-code-analysis - [ ] Blocker: Karaf 4.4.x does not support Java 25 ### Run openHAB installation in Java 25 - [ ] Blocker: Karaf 4.4.x -> still relays on pax logging, calling an unsupported function due to removal of SecurityManager in JDK 25 -> wait for Karaf 4.5 targeted for YE 2025 - [ ] Blocker: Some deprecated methods in JAAS cause Exceptions in JDK25, and need to be replaced. The new API is available in Java 21 (maybe before), but Karaf 4.5 branch needs some more upgrades to work with Java 21 - [ ] Distro has downgraded to bndtools 7.0 due to an issue with Eclipse -> check if 7.2 would work

wurkel · October 23, 2025, 8:43am

Thank you! I had searched in vain for such a reference.