Register Caffeine Cache Collector mBean

[Bernardo]

Hi,

Just added the Caffeine CacheMetricsCollector by following the docs:
https://github.com/prometheus/client_java/tree/11408239035f02a125fe3c860f05fcd0be1e7873#caches

However when I start my application and attach VisualVM to it I can't see the mBeans for the caffeine cache:

I was looking through the CacheMetricsCollector code and I couldn't see the default registry extending some CollectorRegistryMBean.

So I suspect that the cache metrics are not exposed over JMX.

I'm sure I'm getting this really wrong, if anyone know what's the problem with this approach, I'd appreciate some help.