The Java Platform Module System (JPMS; https://www.oracle.com/corporate/features/understanding-java-9-modules.html) has been introduced since Java 9. Cloud SDK for Java and Google API Client Libraries have not adopted the module system.

Example case: #10975

Workaround

Place the Cloud Java SDK in the class path, rather than the module path. The module path and the class path can coexist in a JVM.

References

• gRPC Java is not usable from Java 9 modules grpc/grpc-java#3522 When we evaluated few years ago, it got stuck with this gRPC issue about the module system. Now the issue has been resolved since last year.
• grpc-core and grpc-context jars exporting the same package doesnt go well with OSGI grpc/grpc-java#2727 (comment) For gRPC, a workaround shared by a user was repackaging JAR files.