java 下载代码

1、从文件系统下载到浏览器

　　/**
     * 下载
     * @param res
     * @param fileName
     */
    @RequestMapping(value = "/download", method = RequestMethod.GET)
    public void fileDownload(HttpServletResponse res,String fileName) {
        //设置相应类型为文件
        res.setHeader("content-type", "application/octet-stream");
        res.setContentType("application/octet-stream");
        res.setHeader("Content-Disposition", "attachment;filename=" + fileName);

        //每次读取一个1K
        byte[] buff = new byte[1024];
        BufferedInputStream bis = null;
        OutputStream os = null;
        try {
            //读文件流
            bis = new BufferedInputStream(new FileInputStream(new File(filePath + fileName)));
            //浏览器输出流（下载到浏览器）
            os = res.getOutputStream();
            //读写操作
            int i = bis.read(buff);
            while (i != -1) {
                os.write(buff, 0, buff.length);
                os.flush();
                i = bis.read(buff);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (bis != null) {
                try {
                    bis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

2、使用freemarker从程序下载Exce到l浏览器

/**
 * 下载
 * @param response
 */
@RequestMapping(value = "/export")
    public void export(HttpServletResponse response){
        try {
            //设置导出Excel
            String fileName = "报表_"+dateFormat.format(new Date())+".xls";
            response.setHeader("Content-Disposition", String.format("attachment; filename="%s"", URLEncoder.encode(fileName, "utf-8")));
            response.setContentType("application/vnd.ms-excel;charset=gb2312");

            //加载Excel模板
            Configuration config = new Configuration(Configuration.VERSION_2_3_29);
            config.setObjectWrapper(new DefaultObjectWrapper(Configuration.VERSION_2_3_29));
            config.setDirectoryForTemplateLoading(new File(exportTemplateLoadPath));
            //加载模板
            Template template = config.getTemplate("test.xml");
            OutputStreamWriter outputStreamWriter = new OutputStreamWriter(response.getOutputStream(), StandardCharsets.UTF_8);

            //封装数据
            List<SubData> subDatas = new ArrayList<SubData>();
            subDatas.add(new SubData("1","测试1","软件",1,"套",200,200,"网络"));
            subDatas.add(new SubData("2","测试2","硬件",1,"件",100,100,"试验"));
            subDatas.add(new SubData("3","测试3","书籍",1,"本",100,100,"教育"));
            Data data = new Data("2020年12月8日","100100","张三","男","15559623236","sp.qin@qq.com",30);
            data.setSubDatas(subDatas);

            //构建Map
            Map<String, Data> map = new HashMap<String, Data>();
            map.put("data",data);
            template.process(map,outputStreamWriter);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (TemplateException e) {
            e.printStackTrace();
        }
    }