protobuf-java 4.30.0 at Maven central not compatible with Java 8

[tkeksa]

What version of protobuf and what language are you using?
Version: main/v30.0
Language: Java

What operating system (Linux, Windows, ...) and version?
Windows 10

What runtime / compiler are you using (e.g., python version or gcc version)
Java version: 1.8.0_391, vendor: Oracle Corporation

What did you do?
Build Maven project depending on com.google.protobuf:protobuf-java:4.30.0

What did you expect to see
Successful build

What did you see instead?
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.14.0:compile (default-compile) on project OurService: Compilation failure
[ERROR] /d:/Projects/our-service/src/main/java/cz/company/ucu/backOffice/intens/GrpcDeviceAbstract.java:[75,80] cannot access com.google.protobuf.MessageLite
[ERROR] bad class file: D:\m2_repository\com\google\protobuf\protobuf-java\4.30.0\protobuf-java-4.30.0.jar(com/google/protobuf/MessageLite.class)
[ERROR] class file has wrong version 55.0, should be 52.0

Anything else we should know about your project / environment
All was OK with the 4.29.3 version and no compatibility breaking changes are mentioned in release notes.

[zhangskz]

I think this is normally configured via our javacopts to rules_jvm_external's java_export when creating our release artifacts:

protobuf/build_defs/java_opts.bzl

Lines 8 to 12 in 7a5905d

	JAVA_RELEASE_OPTS = [
	"-source 8",
	"-target 8",
	"-Xep:Java8ApiChecker:ERROR",
	]

We recently noticed that the rules_jvm_external version we are using is no longer compatible with JDK8 which breaks our java/utils and I would guess this is likely the cause here as well. We've reached out here and will try to patch 30.x to keep it JDK 8 compatible, as we still plan to support JDK8 until ~late 2026.

[toddbaert]

Confirm I'm seeing this as well.