Consider how to deal with JDKs which are incompatible with the Gradle version

[tompson]

when selecting Project Gradle - Groovy, Spring Boot 3.5.6 and Java 25 the gradle build does not work because gradle wrapper version 8.14.3 is not compatible with Java 25

* 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

[wilkinsona]

The generated project is configured to use toolchains to compile, run, and test the application. It will work if you run Gradle itself using Java 24 or earlier.

[mhalbritter]

Not sure why @tompson got 8.14.0. We use 8.14.3 by default, and a generated project can be built with JDK 25 as the current JDK.

@tompson is that reproducible?

[tompson]

yes, this is reproducible, when I generate and download this config https://start.spring.io/#!type=gradle-project&language=java&platformVersion=3.5.6&packaging=jar&jvmVersion=25&groupId=com.example&artifactId=demo&name=demo&description=Demo%20project%20for%20Spring%20Boot&packageName=com.example.demo&dependencies=

and then run ./gradlew -version I get

./gradlew -version

------------------------------------------------------------
Gradle 8.14.3
------------------------------------------------------------

Build time:    2025-07-04 13:15:44 UTC
Revision:      e5ee1df3d88b8ca3a8074787a94f373e3090e1db

Kotlin:        2.0.21
Groovy:        3.0.24
Ant:           Apache Ant(TM) version 1.10.15 compiled on August 25 2024
Launcher JVM:  25 (Eclipse Adoptium 25+36-LTS)
Daemon JVM:    /Users/tom/.sdkman/candidates/java/25-tem (no JDK specified, using current Java home)
OS:            Mac OS X 26.0.1 aarch64

and java -version

java -version
openjdk version "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)

the command ./gradlew clean test fails with

./gradlew clean test

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 --info or --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 474ms

[mhalbritter]

Okay, no idea why it behaves that way on your machine, it works on mine:

> ./gradlew -version

------------------------------------------------------------
Gradle 8.14.3
------------------------------------------------------------

Build time:    2025-07-04 13:15:44 UTC
Revision:      e5ee1df3d88b8ca3a8074787a94f373e3090e1db

Kotlin:        2.0.21
Groovy:        3.0.24
Ant:           Apache Ant(TM) version 1.10.15 compiled on August 25 2024
Launcher JVM:  25 (BellSoft 25+37-LTS)
Daemon JVM:    /home/mhalbritter/.sdkman/candidates/java/25-librca (no JDK specified, using current Java home)
OS:            Linux 6.16.10-100.fc41.x86_64 amd64

> ./gradlew clean test
Starting a Gradle Daemon (subsequent builds will be faster)
OpenJDK 64-Bit Server VM warning: Sharing is only supported for boot loader classes because bootstrap classpath has been appended

BUILD SUCCESSFUL in 6s
5 actionable tasks: 4 executed, 1 up-to-date

Please use Java < 25 to run gradle and use the Java Toolchain support which is already in the buildscript.

[mhalbritter]

So @snicoll made me aware that I'm probably the outlier here. It looks like that on Macs, 8.14.3 is not compatible with Java 25. Still wondering why this works on my Linux machine, though.

Maybe we can put something in the help file to instruct people to run Gradle with an older JDK and use the toolchain support to compile with the newer JDK.