How to include additional charsets (via CharsetProvider spi) in Payara

We are in the process of migrating an application from GF4.1 to Payara5. The application processes data from a legacy system that uses a strange charset (ISO464-DE). We found a working solution using JCharset (containing the net.freeutils.charset.CharsetProvider).

In GF4.1 on JDK 8, the charset provider was detected using the spi mechanism if we included the jar in the application war. With Payara on JDK11, this doesn’t work.

We also tried adding the jcharset.jar as a library.

Even including an explicit META-INF/services/java.nio.charset.spi.CharsetProvider in the resources of the war doesn’t change anything.

Has somebody experienced a similar problem, possibly with other SPI?

Thank you.