Java 17 Support

[SethChampagneNRL]

Currently, the Maven configuration for ERDDAP specifies a Java 21 source and target. At least up to ERDDAP v2.25, the code still compiles and runs with Java 17. Some networks that we are running ERDDAP are still running Java 17 and will possibly take a few years to update to Java 21. Java 17 is still LTS through 2029.

Can ERDDAP officially maintain Java 17 compatibility? Is there any technical reasons that make a Java 21 update necessary?

[ChrisJohnNOAA]

Lucene version 10.0.0 requires Java 21. https://lucene.apache.org/core/corenews.html#apache-lucenetm-1000-available

We updated to Lucene 10.0.0 in the 2.25 release. There was a minor code change needed in the migration from 9 to 10. Specifically the Erddap.java changes in this commit: https://github.com/ERDDAP/erddap/pull/219/files#diff-53d85d003a7a63a0ae83c81cb28b8eb661b6e1f64eb524d3d33b5b842a05e50d

I don't believe there was anything else (code in ERDDAP or dependencies) that requires Java 21.

[ChrisJohnNOAA]

I'll have to check if the changes I needed to make for Lucene 10 work with 9.

[ChrisJohnNOAA]

I did some checking (using Java 21) with the current code and Lucene 9. The tests and integration tests all passed. I also ran a Jetty server and manually did some searches and that seemed all set as well.

It seems the only change needed to support Java 17 would be the Java versions and Lucene versions in the pom.

[ChrisJohnNOAA]

Actually there are a handful of switch statements that got updated to use the new pattern matching syntax. Those would need to be changed back for Java 17 support (which is do-able, I believe it was mostly done because the new syntax was much more concise, but there was no functionality change).

[SethChampagneNRL]

That is great news!

[ChrisJohnNOAA]

Code changes for for Java 17 compatibility are here: #241