移动端+SpringBoot后端，解决文件下载不全的问题

1.新建移动端项目，SpringBoot项目。

2.在Controller中添加以下代码

如果在移动端使用了进度条显示，获取了Content-Length，则在后端必须设置

response.setHeader("Content-Length",""+file.length());

 //实现Spring Boot 的文件下载功能，映射网址为/download
    @RequestMapping("/download")
    public String downloadFile(HttpServletRequest request,
                               HttpServletResponse response) throws UnsupportedEncodingException {


        String fileName = "app-debug.apk"; //下载的文件名

        // 如果文件名不为空，则进行下载
        if (fileName != null) {
            //设置文件路径
            String realPath = "D://download/";
            File file = new File(realPath, fileName);

            // 如果文件名存在，则进行下载
            if (file.exists()) {

                // 配置文件下载
                response.setHeader("content-type", "application/octet-stream");
                response.setContentType("application/octet-stream");
                // 下载文件能正常显示中文
                response.setHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(fileName, "UTF-8"));
                response.setHeader("Content-Length",""+file.length());
                // 实现文件下载
                byte[] buffer = new byte[1024];
                FileInputStream fis = null;
                BufferedInputStream bis = null;
                try {
                    fis = new FileInputStream(file);
                    bis = new BufferedInputStream(fis);
                    OutputStream os = response.getOutputStream();
                    int i = bis.read(buffer);
                    while (i != -1) {
                        os.write(buffer, 0, i);
                        i = bis.read(buffer);
                    }
                    System.out.println("Download the song successfully!");
                }
                catch (Exception e) {
                    System.out.println("Download the song failed!");
                }
                finally {
                    if (bis != null) {
                        try {
                            bis.close();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }
                    if (fis != null) {
                        try {
                            fis.close();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }
                }
            }
        }
        return null;
    }