文件下載java實現代碼

1. 通過FileInputStream讀取文件輸入流

    public void export(String excelPath, String fileName) throws Exception{
        
        //將文件存到指定位置
        //讀取目標文件流，轉換調用下載
        File resultFile = new File(excelPath);
        FileInputStream resultFileFi = new FileInputStream(resultFile);
        long l = resultFile.length();
        int k = 0;
        byte abyte0[] = new byte[65000];
        
        // 調用下載
        response.setContentType("application/x-msdownload");
        response.setContentLength((int) l);
        response.setHeader("Content-Disposition", "attachment; filename=" + fileName);
        while ((long) k < l) {
            int j;
            j = resultFileFi.read(abyte0, 0, 65000);
            k += j;
            response.getOutputStream().write(abyte0, 0, j);
        }
        resultFileFi.close();
        
        //轉換成功后，刪除臨時文件
        resultFile.delete();
    }

2. 注意getServletContext().getMimeType(fileName)，讀取文件類型

    public void export1(String excelPath, String fileName){
        if (request.getParameter("file") != null) {
            fileName = request.getParameter("file");
        }
        System.out.println(ServletActionContext.getServletContext().getMimeType(fileName));
        response.setContentType(ServletActionContext.getServletContext().getMimeType(fileName));
        response.setHeader("Content-disposition","attachment; filename="+fileName);
        BufferedInputStream bis = null;
        BufferedOutputStream bos = null;
        try {
            bis = new BufferedInputStream( new FileInputStream(excelPath) );
            bos = new BufferedOutputStream(response.getOutputStream());
            byte[] buff = new byte[2048];
            int bytesRead;
            while(-1 != (bytesRead = bis.read(buff, 0, buff.length))) {
                bos.write(buff,0,bytesRead);
            }
         } catch(final IOException e) {
            System.out.println ( "出現IOException." + e );
         } finally {
            if (bis != null)
                try {
                    bis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            if (bos != null)
                try {
                    bos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
         }        
    }