JEP 472: Prepare to Restrict the Use of JNI

[ChengJin01]

Summary (from https://openjdk.org/jeps/472)

Issue warnings about uses of the Java Native Interface (JNI) and adjust warnings from the Foreign Function & Memory (FFM) API to be consistent with JNI. All such warnings aim to prepare developers for a future release that provides integrity by default by uniformly restricting JNI and the FFM API. Application developers can avoid current warnings and future restrictions by selectively enabling the interaction of Java and native code where it is critical to the application.

Goals

• Preserve the status of JNI as a standard way to interoperate with native code.
• Prepare the Java ecosystem for a future release that disallows interoperation with native code by default, whether via JNI or the FFM API. As of that release, application developers will have to explicitly enable the use of JNI and the FFM API at startup.
• Align the use of JNI and the FFM API so that library maintainers can migrate from one to the other without changing any command line options.

FYI: @tajila, @pshipton

[ChengJin01]

The JEP is still in the Candidate status (which is not targeted for JDK23) but the related code has been implemented via https://bugs.openjdk.org/browse/JDK-8331671. So it is expected to be merged to the repo soon if no more concerns in there.

[pshipton]

We'll assume Java 24 for now.