If you haven't browse through Netflix OSS github repositories yet, you should do it immediately. It would be very surprising if you could not find something useful there.
I've found three projects (Feign, Hystrix, Archaius) that address directly the same problem that I've been building similar library to solve. Many others are inspirational or interesting at least, like RxJava quite popular in "reactive circles".
Some of them may have (better?) alternatives like Retrofit, some other are used as bricks in interesting projects like Halfpipe.
Apparently everybody is going crazy about Spring Boot. Let's hope it will not share destiny with Spring Roo.