public int doStartTag() throws JspException {
        final int rc = super.doStartTag();
        final FacesContext context = FacesContext.getCurrentInstance();
        AssertionUtil.assertNotNull("FacesContext", context);
        final String encoding = PageContextUtil
                .getCharacterEncoding(pageContext);
        pageContext.getResponse().setLocale(context.getViewRoot().getLocale());
        final String acceptContentTypes = WebAppUtil.getAcceptHeader(context);
// >> 追加
        if( acceptContentTypes != null)
        {
// <<追加
        final String contentType = ContentTypeUtil
                .getContentType(acceptContentTypes);
        pageContext.getResponse().setContentType(
                contentType + "; charset=" + encoding);
// >> 追加
        }
// <<追加