Are there any plans to officially support Java 21 in upcoming releases?

[alegro-hub]

Hi Hop community,

I’m currently exploring the possibility of running Apache Hop with Java 21. I understand that Java 17 is officially supported, but I’d like to know if anyone has successfully run Hop on Java 21, or if there are any known issues or limitations.

Are there any plans to officially support Java 21 in upcoming releases?

Thanks in advance for your insights!

[hansva]

Everything "should" work in Java 21. We just don't run tests in it so we can't really call it officially supported. We depend a lot on our dependencies, which also influenced when we could move to Java 17

[alegro-hub]

Hi, thank you very much for your response.
I'd like to confirm my understanding and ask a few follow-up questions.

1. When you mentioned that it “should work” on Java 21 — is that expectation mainly based on Java’s strong backward compatibility?
   (i.e., since Hop runs on Java 17, it’s expected to work on 21 as well.)

2. Am I understanding correctly that even if Hop itself works on Java 21,
   the team cannot officially declare support until all third-party libraries Hop depends on are also confirmed to be compatible?
   In other words, the current limitation of supported Java versions is mainly due to dependency compatibility, not Hop’s core?

Additionally, could you please clarify a couple more points?

3. Are there any current plans or timelines for officially testing or supporting Java 21?

4. Looking ahead, does the Hop project plan to align its support with Java LTS releases (e.g., 17 → 21 → 25)?

Thank you again for your time and clarification.

[hansva]

1. Yes, we have no builds or tests against Java 21, but as with most Java versions, it has very strong backwards compatibility.

2. As we can run pipelines in other engines such as Spark, Flink, and Dataflow, those platforms first need to support the required Java version or higher before our pipelines can be executed there. Our Java 17 upgrade was fully tested before we did an actual release because we had to wait for the engines to support it.

3. No, there are no plans. Java 17 EOL is planned for September 2027. We still have 2 years to decide what we will do

4. We will only be using LTS releases, but we might not follow the path you have painted out. Depending on what other projects decide, it could be that 21 is being skipped, and we will move from 17 -> 25. Mainly to avoid having to do another upgrade/test only a year after the move to 21. I think I have seen other projects think about this.

[alegro-hub]

Thank you for the detailed explanation — that makes perfect sense.
I understand now that Hop itself may run fine on Java 21 due to Java’s strong backward compatibility,
but the official support depends on the external engines (like Spark, Flink, and Dataflow) and their Java compatibility.

Thanks again for clarifying the roadmap and support policy!