I came across this problem recently and couldn't find the answer here. I'm using Weblogic and most of the solutions are for Tomcat.
For encoding to work with Weblogic you have to put this to your weblogic.xml
/*
UTF-8
Source: weblogic.xml docs
NOTE: I also have these options in my _JAVA_OPTIONS, but don't know if they are necessary.
-Dweblogic.webservice.i18n.charset=utf-8
-Dfile.encoding=UTF-8