I have to use attached diff to successfully merge.
Created attachment 90138 [details, diff] add package spec to Proxy (ambiguous java.lang.reflect.Proxy and java.net.Proxy)
Created attachment 94336 [details, diff] hessian-3.0.8-r3.ebuild.patch Ebuild using that patch
Created attachment 94337 [details, diff] files/hessian-3.0.8-jdk15.patch
It also seems that upstream has also released version 3.0.20 that uses 1.5 features.
3.0.20 does not fit the same slot probably so I applied your patch. Sorry that it took so long.