Java 9 is an unusually-complex Java release. It comes with deep changes to some long-held norms, compatibility-breaking changes at build time and run time, and a new release cadence. There's a lot of great stuff, but development teams face tough decisions about what to migrate, how to migrate it, and when to do so.
Here at PreEmptive, we have an especially-complex problem because our flagship Java application, DashO, runs on the Java platform, integrates deeply with the Java platform, and supports apps developed with nearly all versions and implementations of the Java platform. DashO's migration to Java 9 requires deep understanding and extensive care to ensure that DashO continues to be able to inspect, obfuscate, and inject code into apps across all those platforms, while preserving behavior, performance, stability, and portability.
So we've been hard at work on our own migration plans, and we want to share what we've learned. Hopefully this article will make your Java 9 migration planning a little easier.