java文件下载的几种方式

电玩女神 2021-11-05 06:02 370阅读 0赞

### 1.流形式下载.下载服务器本地磁盘文件到本地选择文件夹 ###

public HttpServletResponse download(String path, HttpServletResponse response) {
            try {
                // path是指欲下载的文件的路径。
                File file = new File(path);
                // 取得文件名。
                String filename = file.getName();
                // 取得文件的后缀名。
                String ext = filename.substring(filename.lastIndexOf(".") + 1).toUpperCase();
    
                // 以流的形式下载文件。
                InputStream fis = new BufferedInputStream(new FileInputStream(path));
                byte[] buffer = new byte[fis.available()];
                fis.read(buffer);
                fis.close();
                // 清空response
                response.reset();
                // 设置response的Header
                response.addHeader("Content-Disposition", "attachment;filename=" + new String(filename.getBytes()));
                response.addHeader("Content-Length", "" + file.length());
                OutputStream toClient = new BufferedOutputStream(response.getOutputStream());
                response.setContentType("application/octet-stream");
                toClient.write(buffer);
                toClient.flush();
                toClient.close();
            } catch (IOException ex) {
                ex.printStackTrace();
            }
            return response;
        }

## ##

### 2.根据网络地址下载文件到本地 ###

public void downloadNet(HttpServletResponse response) throws MalformedURLException {
            // 下载网络文件
            int bytesum = 0;
            int byteread = 0;
            //文件网络地址
            URL url = new URL("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1565257066249&di=48096d53b98d3a8f049fdadedfbcc9da&imgtype=0&src=http%3A%2F%2Fpic13.nipic.com%2F20110409%2F7119492_114440620000_2.jpg");
            try {
                URLConnection conn = url.openConnection();
                InputStream inStream = conn.getInputStream();
                FileOutputStream fs = new FileOutputStream("d:/abc/abc.png"); //存储本地位置
    
                byte[] buffer = new byte[2048];
                int length;
                while ((byteread = inStream.read(buffer)) != -1) {
                    bytesum += byteread;
                    System.out.println(bytesum);
                    fs.write(buffer, 0, byteread);
                }
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

### 3.下载服务器本地文件到本地,开启预览模式 ###

public void downLoad(String filePath, HttpServletResponse response, boolean isOnLine) throws Exception {
            File f = new File(filePath);
            if (!f.exists()) {
                response.sendError(404, "File not found!");
                return;
            }
            BufferedInputStream br = new BufferedInputStream(new FileInputStream(f));
            byte[] buf = new byte[1024];
            int len = 0;
    
            response.reset(); // 非常重要
            if (isOnLine) { // 在线打开方式
                URL u = new URL("file:///" + filePath);
                response.setContentType(u.openConnection().getContentType());
                response.setHeader("Content-Disposition", "inline; filename=" + f.getName());
                // 文件名应该编码成UTF-8
            } else { // 纯下载方式
                response.setContentType("application/x-msdownload");
                response.setHeader("Content-Disposition", "attachment; filename=" + f.getName());
            }
            OutputStream out = response.getOutputStream();
            while ((len = br.read(buf)) > 0)
                out.write(buf, 0, len);
            br.close();
            out.close();
        }