【工具类】Java后台上传下载文件的几种方式

/**
 * 通过 HTTP PUT 请求将 JPG 照片上传至指定的腾讯云地址
 * 协议要求:
 * 

 * PUT / HTTP/1.1
 * Host: xxx.myqcloud.com //腾讯提供的Host地址
 * Authorization: Auth String //每个图片的上传token，有效期为订单下发开始24h
 * [Object Content] //二进制照片内容
 */
public void uploadImage(String localImagePath) throws Exception {
    // 1.将照片上传至腾讯地图众包侧提供的云服务上
    try {
        File imageFile = new File(localImagePath);
        if (imageFile.exists()) {
            String url = "http://" + mapVendor.getHost() + mapVendorImageDetail.getBackUrl();
            HttpHeaders headers = new HttpHeaders();
            headers.set("Content-Type", "image/jpeg");
            headers.add("Host", mapVendor.getHost());
            headers.add("Authorization", mapVendorImageDetail.getBackAuth());
            restTemplate.put(url, new HttpEntity(new FileSystemResource(imageFile), headers));
        }
    } catch (RestClientException e) {
        // 2.使用捕获异常来处理返回的非200的状态响应,如果非200则认定上传失败
        logger.error("send local image [" + localImagePath + "] to tencent error", e);
    }
}

/**
 * 以流的方式下载
 * @param path 欲下载的文件的路径
 * @param response 响应内容
 *
 */
public void 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();
        // 获取下载文件的输入流
        InputStream inputStream = new BufferedInputStream(new FileInputStream(file));
        byte[] buffer = new byte[inputStream.available()];
        inputStream.read(buffer);
        inputStream.close();
        // 清空response
        response.reset();
        // 重新设置response
        response.setContentType("application/octet-stream");
        response.addHeader("Content-Disposition", "attachment;filename=" + new String(filename.getBytes()));
        response.addHeader("Content-Length", "" + file.length());
        // 写入下载文件的输出流
        OutputStream outputStream = new BufferedOutputStream(response.getOutputStream());
        outputStream.write(buffer);
        outputStream.flush();
        outputStream.close();
    } catch (IOException ex) {
        //TODO 记录日志并做相关业务
    }
}

/**
 * 把网络上的图片保存到本地
 */
public void downloadNet() throws Exception {
    // 下载网络文件
    int byteSum = 0;
    int byteRead;

    URL url = new URL("https://www.baidu.com/img/PCtm_d9c8750bed0b3c7d089fa7d55720d6cf.png");
    URLConnection conn = url.openConnection();
    InputStream inputStream = conn.getInputStream();
    FileOutputStream fileOutputStream = new FileOutputStream("c:/logo.gif");
    // 存放读取的字节
    byte[] buffer = new byte[1204];
    while ((byteRead = inputStream.read(buffer)) != -1) {
        byteSum += byteRead;
        System.out.println(byteSum);
        fileOutputStream.write(buffer, 0, byteRead);
    }
}

/**
 * 把网络上的图片保存到本地并支持在线打开
 */
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();
    }