Apache Pekko doesn't support autogenerated TLS certs about playframework HOT 1 CLOSED

This has nothing to do with Pekko nor Akka.
The exception is caused by the upgrade to Java 17. We already mention this in the Play 2.9. release highlights (see "Please be aware that..." in the linked section) which links to the migration guide which describes the --add-exports=... workaround for Java 17 (which does not work for Java 21 unfortunately however...)

In the end this is a lack of documentation, which I am fixing with

• #12563

In that PR I add the same note linked above on the highlights page to the section you referenced on the Configuring HTTPS page.
Also I enhanced the migration notes to show how to apply the flag in dev mode and when staging/packaging the application for production use.

Using your snippets, you have to use:

<my-project-executable> -Dhttp.port=disabled -Dhttps.port=9443 -Dpidfile.path=/dev/null -Dlogger.resource=dev-logback.xml -J--add-exports=java.base/sun.security.x509=ALL-UNNAMED

sbt -J"-Dhttp.port=disabled" -J"-Dhttps.port=9443" -J"--add-exports=java.base/sun.security.x509=ALL-UNNAMED" run

Just take a look at my PR to see other approaches.

from playframework.