Struts 2 - parametros result type

public class MyExampleFileDownload extends DownloadAction{


protected StreamInfo getStreamInfo(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws Exception {

// File Name
String fileName = mapping.getParameter();

// Set the content disposition
response.setHeader("Content-disposition",
"attachment; filename=" + fileName);

// Download a "pdf" file - gets the file name from the
// Action Mapping's parameter
String contentType = "application/pdf";
File file = new File(fileName);

return new FileStreamInfo(contentType, file);

}
}

<action name="mydownload" class="DownloadAction">
      <result name="mystream" type="stream">
	      <param name="contentType">${myContentType}</param>
	      <param name="contentLength">${myContentLength}</param>
	      <param name="contentDisposition">${myContentDisposition}</param>
	      <param name="inputName">myInputStream</param>
      </result>
    </action

public class DownloadAction {
    
    private Myfile myfile; 
    private Long id;

    // ----- Simple Getters / Setters
    
    public Long getId() {
        return this.id;
    }
    public void setId(Long id) {
        this.id = id;
    }

    // ----- StreamResult Stuff
    
    public String getMyContentType() {
    	return myfile.getFileType();
    }
    public Integer getMyContentLength() {
    	return myfyle.getFileSize();
    }
    public String getMyContentDisposition() {
    	return "filename=\"" + myfile.getFileName() +"\"";
    }
    public InputStream getMyInputStream() {
    		return new ByteArrayInputStream(myfile.getArchive());
    }
    
    // ----- Myfile stuff
    
    public Myfile getMyfile() {
        return myfile;
    }
    public void setMyfile(Myfile user) {
        this.myfile = myfile;
    }

    //********************************* Control Methods

    public String execute() {
        setMyfile(DAO.findMyFile(this.id));
    	return "mystream";
    }

}