Struts2文件流下载

	String filePath=getRequest().getParameter("file");
		String fileName = getRequest().getParameter("fileName");
		String  id = getRequest().getParameter("id");
	 	filePath = getRequest().getRealPath("")+"\\"+"WordToPDF\\"+id+".pdf";
	 	File f = new File(filePath);
		if(fileName==null){
			fileName=id;
		}
			
	 	InputStream is=null;
        OutputStream os=null;
		try{
	         /**//*解决中文乱码问题，设置后产生一个新的String对象此对象以改变了编码*/
	         
	         byte[] b=new byte[1024];
	         int i=0;
             is = new FileInputStream(f);
             os = getResponse().getOutputStream();
             /**//*设置报头信息，弹出窗口中显示的文件名    newpath*/
             getResponse().setCharacterEncoding("utf-8");
             fileName = fileName+filePath.substring(filePath.lastIndexOf("."));
             String agent = (String)getRequest().getHeader("USER-AGENT");
             if(agent != null && agent.indexOf("MSIE") == -1) {
             // FF
	             fileName = "=?UTF-8?B?" + (new String (Base64.encodeBase64(fileName.getBytes("UTF-8")))) + "?=";
	             getResponse().setHeader("Content-Disposition", "attachment; filename=" + fileName);
             }else {
             // IE
	             fileName = new String(fileName.getBytes("GBK"), "ISO-8859-1");
	             getResponse().setHeader("Content-Disposition", "attachment; filename=" + fileName);
             }
             //设置文件大小
             getResponse().setContentLength((int) f.length());
             /**//*具体的输入输出流操作*/
             while((i=is.read(b))!=-1){
                 os.write(b, 0, i);
             }
         } catch (IOException e){
             // TODO Auto-generated catch block
             e.printStackTrace();
         }finally{
             os.flush();
             os.close();
             is.close();
         }
/*         if(f.exists()){
        	 f.setWritable(true);
        	 f.delete();
         }	*/