grpc-java: Dropping support for Java 7

[Eric Anderson]

TL;DR: Dropping support for Java 7, but keeping current Android API level. If this causes problems for you, please reply here or comment on the issue.

gRPC Java desperately wants Java 8 language features to design more natural APIs and provide more convenience when implementing. Some of our dependencies are also looking at dropping Java 7 support. To our knowledge, there is limited need for Java 7.

Issue 4671 is tracking dropping support for Java 7 in order to use Java 8 language features. Java 8 JDK library use will continue to be limited to continue our Android support, in the same fashion as Java 7. No changes in Android support are included with this change.

If this would negatively impact you, please reach out to us on the issue. We want to better understand the constraints of our users. If you are needing Java 7 support simply to avoid dropping support in your own product, that is useful information, but it would be even better if you knew whether your users were actually using Java 7 in production and the likelihood they would upgrade to a new release.

We're planning to keep Java 7 support in io.grpc.Context for the near future, at least until we see how the rest of the process goes. If you need Java 7 for grpc-context, please still discuss with us so we have an idea of your needs.

If you need Java 7 support, please contact us within 2 weeks to help the planning process. Later is better than never, but early is extremely helpful. It is unlikely v1.34 will require Java 8, but you should assume that any future release might require Java 8 if you don't contact us.