A built-in Spring cache adapter would be great! I'm not a fan of JCache and I was pleasantly surprised by how simple your Guava adapters were to base this on, so much so that adding myself to the author tag was probably premature. =)
I was just informed that Spring Boot configures using Guava's CacheBuilderSpec. I hadn't seen it used anywhere but internal to Google and haven't had the pleasure of using Spring since the 2.x days. If that would simplify integration then I can add a CaffeineSpec that mirrors Guava's.
I don't think that's necessary Ben. Spring Boot simply integrates with the API at hand. Once your PR is merged, I'll integrate caffeine support in Spring Boot 1.4 right the way. If you have ideas to smooth the integration for Spring Boot users, feel free to reach out.