I'm using Struts 2 with Struts 2 JSON Plugin. When I deploy my application on a Linux box and the JVM file.encoding parameter is set to ISO-8859-1 the json content is generated as UTF-8 and the content type is application/json;charset=iso-8859-1. So to workaround this problem I set the defaultEncoding attribute to UTF-8 to fix it on Redhat Linux. But if I run this configuration on windows with the defaultEncoding attribute I get the json content with what it looks to be iso-8859-1 encoding and content type application/json;charset=utf-8.
To replicate the problem on Windows you can set defaultEncoding to utf-8.