[jira] [Created] (FLINK-24634) Java 11 profile should target JDK 8

["Chesnay Schepler (Jira)" <ji...@apache.org>]

Chesnay Schepler created FLINK-24634:
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             Summary: Java 11 profile should target JDK 8
                 Key: FLINK-24634
                 URL: https://issues.apache.org/jira/browse/FLINK-24634
             Project: Flink
          Issue Type: Technical Debt
          Components: Build System
            Reporter: Chesnay Schepler
            Assignee: Chesnay Schepler
             Fix For: 1.15.0


Thee {{java11}} profile currently targets Java 11. This was useful because we saw that doing so reveals additional issues that are not detected when building for Java 8. The end goal was to ensure a smooth transition once we switch.

However, this has adverse effects on developer productivity.

If you happen to switch between Java versions (for example, because of separate environments, or because certain features require Java 8), then you can easily run into UnsupportedVersionErrors when attempting to use Java 8 with Java 11 bytecode.

IntelliJ also picks up on this and automatically sets the language level to 11, which means that it will readily allow you to use Java 11 exclusive APIs that will fail on CI later on.

To remedy this I propose to split the profile.

The {{java11}} profile will pretty much stay as is, except that it is targeting java 8. The value proposition of this profile is being able to build Flink for Java 8 with Java 11.
A new explicitly-opt-in {{java11-target}} profile then sets the target version to Java 11, which we will use on CI. This profile will ensure that we can readily switch to Java 11 as the target in the future.




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