文件下载java实现代码详解编程语言

1. 通过FileInputStream读取文件输入流

    public void export(String excelPath, String fileName) throws Exception{ 
         
        //将文件存到指定位置 
        //读取目标文件流，转换调用下载 
        File resultFile = new File(excelPath); 
        FileInputStream resultFileFi = new FileInputStream(resultFile); 
        long l = resultFile.length(); 
        int k = 0; 
        byte abyte0[] = new byte[65000]; 
         
        // 调用下载 
        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(); 
         
        //转换成功后，删除临时文件 
        resultFile.delete(); 
    }

2. 注意getServletContext().getMimeType(fileName)，读取文件类型

    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 ( "出现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(); 
                } 
         }         
    }