In order to support running in a portlet, it's imperative the core, component, and application related code use standard JSF APIs whenever possible and avoid any casting to classes or using methods that are not agnostic to the environment they are running in.

In the various ACE exporter classes (CSVExporter, PDFExporter, XMLExporter, ExcelExporter) we have code that looks like this (from CSVExporter.export):

...
HttpServletResponse response = (HttpServletResponse) facesContext.getExternalContext().getResponse();
OutputStream os = response.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os , encodingType);
PrintWriter writer = new PrintWriter(osw);
...
     response.setContentType("text/csv");
     response.setHeader("Expires", "0");
        response.setHeader("Cache-Control","must-revalidate, post-check=0, pre-check=0");
        response.setHeader("Pragma", "public");
        response.setHeader("Content-disposition", "attachment;filename="+ filename + ".csv");
        
        writer.flush();
        writer.close();
        
        response.getOutputStream().flush();
}

Casting to HttpServletResponse causes a problem when running in a portlet. The JSF way to do this which avoids the casting exception with portlets:

...
        ExternalContext ec = facesContext.getExternalContext();
OutputStream os = ec.getResponseOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os , encodingType);
PrintWriter writer = new PrintWriter(osw);
...
     ec.setResponseContentType("text/csv");
     ec.setResponseHeader("Expires", "0");
        ec.setResponseHeader("Cache-Control", "must-revalidate, post-check=0, pre-check=0");
        ec.setResponseHeader("Pragma", "public");
        ec.setResponseHeader("Content-disposition", "attachment;filename=" + filename + ".csv");
        
        writer.flush();
        writer.close();
        
        os.flush();
}

All of the current exporters I noted need to have this corrected. Perhaps some common code could be lifted up to the parent abstract Exporter class.