Matthew Ernst created FLINK-34658:
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Summary: Scala API unusable on Flink 1.18.1/Java 17 Docker image
Key: FLINK-34658
URL: https://issues.apache.org/jira/browse/FLINK-34658
Project: Flink
Issue Type: Bug
Components: API / Scala
Affects Versions: 1.18.1, 1.18.0
Environment: This bug has been reproduced under macOS (Intel x64) and
Linux (AMD 64) on a Flink cluster running in session mode.
Reporter: Matthew Ernst
The Scala API should still work in Flink 1.18. The official Docker image for
Flink 1.18.1 on Java 17 ("flink:1.18.1-scala_2.12-java17") causes jobs using
the Scala API to immediately throw a ReflectiveOperationException. Jobs using
the Scala API still work correctly on the Java 11 image
("flink:1.18.1-scala_2.12-java11").
The problem happens because the flink-scala JAR file included in the image
("flink-scala_2.12-1.18.1.jar") has been built with an old Scala compiler that
has a [compatibility bug with Java
17|https://github.com/scala/bug/issues/12419]. Rebuilding the flink-scala JAR
file with the Scala compiler set to 2.12.15 or later fixes the bug. At my day
job I cannot use Java 11 for a particular Flink job due to dependency on a Java
library that uses [Java records|https://openjdk.org/jeps/395] (introduced in
Java 16).
I have created a github repository with an example application and a longer
description of the bug and how to fix it with a newer Scala compiler version:
https://github.com/mattbernst/scala-java17-flink
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