Servlet下載下傳檔案

java中下載下傳檔案最好用servlet，我在用普通的類實作下載下傳功能時提示getOutputStream has already been commit 的error，查了好多資料都沒有解決，（有的說response要reset，有的說jsp頁面中不能換行等等，我試過後都不行）用servlet來做則不會有這個問題，源代碼如下：

 public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        String fileName = (String) request.getParameter("fileName");

        String path = "/dept/hr/files/training/" + fileName;

        String realPath = this.getServletContext().getRealPath(path);

        File f = new File(realPath);

        if (!f.exists()) {

            response.sendError(404, "File not found!");

            return;

        }

       fileName = new String(fileName.getBytes("GB2312"), "ISO8859_1"); //處理檔案中含中文的問題,不是萬能的

        boolean isOnLine = false;

        response.reset(); //非常重要

        if (isOnLine) { //線上打開方式

            URL u = new URL("file:///" + realPath);

            response.setContentType(u.openConnection().getContentType());

            response.setHeader("Content-Disposition",

                               "inline; filename=" + f.getName());

        } else { //純下載下傳方式

            response.setContentType("application/x-msdownload");

            response.setHeader("Content-Disposition",

                               "attachment; filename=" + fileName);

        }

        byte[] buf = new byte[1024];

        int len = 0;

        BufferedInputStream br = null;

        OutputStream out = null;

        try {

            br = new BufferedInputStream(new FileInputStream(f));

            out = response.getOutputStream();

            while ((len = br.read(buf)) > 0) {

                out.write(buf, 0, len);

            }

            out.flush();

        } catch (Exception e) {

            //e.printStackTrace();

        } finally {

            if (br != null) {

                br.close();

                br = null;

            }

            if (out != null) {

                out.close();

                out = null;

            }

        }

    }

本源代碼是基于axman的版本，根據實際需要稍微改了改，我用的是weblogic，當下載下傳.xls等檔案時如果使用者選擇取消則有時報Connection reset by peer:socket write error,其他類型如.doc檔案則不會出錯，tomcat下不知道有沒有這個問題，網上查了半天不知是以然，但有一點可以肯定，就是它并不影響程式的正常運作，是以我把錯誤輸出語句注釋掉了。