The org.apache.struts2.dispatcher.ng.filter.StrutsPrepareFilter --> org.apache.struts2.dispatcher.Dispatcher.prepare(HttpServletRequest request, HttpServletResponse response) is calling response.setLocale(locale) when you specify a default locale (using struts.properties struts.locale). This is wrong because consider the following example:
This is a static resource stored in the following path: www.mydomain.com/myApp/scripts/utils.js where myApp is the webcontext and /scripts/utils.js is a java script file.
1. A request to /myApp/scripts/utils.js.
1. Even though Struts 2 is not going to handle the request org.apache.struts2.dispatcher.ng.filter.StrutsPrepareFilter calls prepare.setEncodingAndLocale(request, response);
which sets the Request Encoding and the Response Locale.
2. Servlet Container Response setLocale obtains the character encoding corresponding to that locale and assign a character encoding to the response. This behavior is correct according to the spec: http://download.oracle.com/javaee/5/api/javax/servlet/ServletResponse.html#setLocale%28java.util.Locale%29
3. Struts Execute filter doesn't handle the request so chain.doFilter(request, response); is called.
4. Once all filters are called the servlet container DefaultServlet is called to handle the request and send the content of the file assigning the response header Content-Type in which this case it will use the encoding type that was set before by the StrutsPrepareFilter. This might not correspond to the actual encoding of the file.
An example of the Header Response Content-Type:
This only happens when you specify the default locale in the struts.properties because of these lines in Dispatcher.prepare():
I think that locale = LocalizedTextUtil.localeFromString(defaultLocale, request.getLocale()); should be removed because setting locale will set the character encoding. And this has side effects when requests are made to static resources.