There is an offical Docker Image which is based on OpenJDK:8. But as a matter of fact, atlassian only supports the Oracle Java.
So, this build is been updated to make of for the java problem and is currently using 'Confluence:6.0.1' as its base.
You probobly need to build the Oracle Java:8 first.
It is a pretty streight forward build, as usuall:
$ docker build --tag=confluence:6.0.1 --force-rm --no-cache .