Building openjfx

[Kevin Rushforth]

Ah yes, you are running into one of the charming issues with using 
gradle: namely, gradle is slow in supporting the latest JDKs.

The easiest way is to use JDK 24.x (e.g., 24.0.2) to both run gradle and 
build JavaFX. This is what we do.

If you need to use JDK 25 to build, you will need two JDKs: one to run 
gradle (JDK 24 or earlier) and another to use for building. Point 
JAVA_HOME to the JDK used to launch gradle and put it in your PATH. 
Point JDK_HOME to the JDK 25 that you will use to build JavaFX.

-- Kevin



On 10/13/2025 5:22 PM, Orion Poplawski wrote:
> So I'm stepping back to simply try building openjfx with gradlew but I 
> get:
>
> $ sh gradlew --info build
> Initialized native services in: /home/orion/.gradle/native
> Initialized jansi services in: /home/orion/.gradle/native
> The client will now receive all logging from the daemon (pid: 253483). 
> The daemon log file: 
> /home/orion/.gradle/daemon/8.14.2/daemon-253483.out.log
> Starting 2nd build in daemon [uptime: 2 mins 22.763 secs, performance: 
> 97%, GC rate: 0.00/s, heap usage: 2% of 512 MiB, non-heap usage: 9% of 
> 384 MiB]
> Using 6 worker leases.
> Now considering [/home/orion/openjfx-25/jfx25u-25-29] as hierarchies 
> to watch
> Now considering [/home/orion/openjfx-25/jfx25u-25-29/buildSrc, 
> /home/orion/openjfx-25/jfx25u-25-29] as hierarchies to watch
> Watching the file system is configured to be enabled if available
> File system watching is active
> Starting Build
> Caching disabled for Groovy DSL script compilation (settings) because:
>   Build cache is disabled
>   Not worth caching.
> Compiling settings file 
> '/home/orion/openjfx-25/jfx25u-25-29/settings.gradle' using 
> BuildScriptTransformer.
>
> FAILURE: Build failed with an exception.
>
> * What went wrong:
> BUG! exception in phase 'semantic analysis' in source unit 
> '_BuildScript_' Unsupported class file major version 69
> > Unsupported class file major version 69
>
> * Try:
> > Run with --stacktrace option to get the stack trace.
> > Run with --debug option to get more log output.
> > Run with --scan to get full insights.
> > Get more help at https://help.gradle.org.
>
> BUILD FAILED in 466ms
>
> $ java --version
> openjdk 25 2025-09-16
> OpenJDK Runtime Environment (Red_Hat-25.0.0.0.36-1) (build 25+36)
> OpenJDK 64-Bit Server VM (Red_Hat-25.0.0.0.36-1) (build 25+36, mixed 
> mode, sharing)
>
> What am I doing wrong?
>