Test against JDK 17, 21 and 25 in CI

[davidpavlovschi]

Addresses the remaining unchecked Patch item in #74: "Test on Java 8 and latest Java version to ensure compatibility as versions are released".

What changes

.github/workflows/maven_test.yml currently pins a single toolchain (Set up JDK 17, java-version: 17), so nothing catches a regression that only shows up on a newer JDK until a user reports it. This adds a fail-fast: false matrix over java: [ 17, 21, 25 ], renames the job to Test (JDK ${{ matrix.java }}) so the three legs are distinguishable in the checks list, and runs the existing ./mvnw clean verify -P integration-test unchanged on each.

The Maven cache key gains a jdk${{ matrix.java }} segment (${{ runner.os }}-m2-jdk17-<hash> etc.). Without it the three parallel legs on master all try to save ${{ runner.os }}-m2-<hash>, so two of the three actions/cache saves would collide on the same key ("Unable to reserve cache … already exists") and the legs would keep overwriting one shared entry. Cache behaviour on the GitHub runners is the one part of this change that can only be exercised once it runs on master.

Only the workflow file changes; no source, no pom.xml, no dependency versions.

Why Java 8 is not in the matrix

The issue asks for a Java 8 leg, but the toolchain cannot be JDK 8 in this repo:

• pom.xml declares compile-java-9 (<release>9</release>) and compile-java-17 (<release>17</release>) executions for the multi-release jar, and maven-javadoc-plugin is configured with <source>17</source>.
• tools.jackson.core:jackson-databind 3.2.1 is a provided-scope dependency (so it is on the compile and test classpath) and Jackson 3 has a Java 17 baseline.

So 17 is the floor for building. The Java 8 target is already enforced independently of the toolchain by <release>${java.version}</release> (java.version = 8) on the default-compile execution — --release 8 is what makes javac reject post-8 APIs, and it does that identically on a JDK 17, 21 or 25 toolchain. Adding a JDK 8 leg would not test anything the existing release 8 setting does not already cover, and it cannot be done without dropping Jackson 3 support.

One thing the new legs surface that is worth knowing about: on JDK 21 and 25, javac emits source value 8 is obsolete and will be removed in a future release / target value 8 is obsolete … (2 occurrences each). JDK 17 does not. That is a warning today, but it is the signal for when the Java 8 target will actually need to be revisited, and having 21/25 in CI is what makes it visible.

Verified

All three matrix legs were run locally with the exact workflow command, each on the matching Temurin JDK (macOS 27.0 / aarch64, not the ubuntu-latest runner):

• ./mvnw clean verify -P integration-test on Temurin 17.0.20+8 — exit 0, Tests run: 317, Failures: 0, Errors: 0, Skipped: 4, invoker Passed: 3, Failed: 0, Errors: 0, Skipped: 0, BUILD SUCCESS.
• Same command on Temurin 21.0.12+8 — exit 0, Tests run: 317, Failures: 0, Errors: 0, Skipped: 4, invoker Passed: 3, Failed: 0, Errors: 0, Skipped: 0, BUILD SUCCESS.
• Same command on Temurin 25.0.1 — exit 0, Tests run: 317, Failures: 0, Errors: 0, Skipped: 4, invoker Passed: 3, Failed: 0, Errors: 0, Skipped: 0, BUILD SUCCESS.

The workflow file also parses as YAML with the expected strategy: {fail-fast: false, matrix: {java: [17, 21, 25]}}.

Not verified locally: the cache hit/miss behaviour on the GitHub runners — that only exercises once this runs on master.

If you would rather keep CI to two legs (17 + latest) to hold runner minutes down, dropping 21 from the list is the only edit needed.

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Summary by cubic

Expand CI to test on JDK 17, 21, and 25 to catch Java-version regressions and meet #74. Adds per-JDK cache keys and clearer job names; Maven command stays the same.

• Refactors
  • Adds matrix java: [17, 21, 25] with fail-fast: false; job renamed to "Test (JDK ${{ matrix.java }})".
  • Cache keys include jdk${{ matrix.java }} to avoid collisions across parallel runs.
  • JDK 17 is the build floor (multi-release build, jackson-databind 3.x); Java 8 target stays enforced via --release 8, so no JDK 8 CI leg.

^{Written for commit 7c176d6. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 1 file

_{Re-trigger cubic}