JAVA实现下载文件功能的两种方法

第一种方法：

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;
 }

 public void downloadLocal(HttpServletResponse response) throws FileNotFoundException {
  // 下载本地文件
  String fileName = "Operator.doc".toString(); // 文件的默认保存名
  // 读到流中
  InputStream inStream = new FileInputStream("c:/Operator.doc");// 文件的存放路径
  // 设置输出的格式
  response.reset();
  response.setContentType("bin");
  response.addHeader("Content-Disposition", "attachment; filename="" + fileName + """);
  // 循环取出流中的数据
  byte[] b = new byte[100];
  int len;
  try {
   while ((len = inStream.read(b)) > 0)
    response.getOutputStream().write(b, 0, len);
   inStream.close();
  } catch (IOException e) {
   e.printStackTrace();
  }
 }

 public void downloadNet(HttpServletResponse response) throws MalformedURLException {
  // 下载网络文件
  int bytesum = 0;
  int byteread = 0;

  URL url = new URL("windine.blogdriver.com/logo.gif");

  try {
   URLConnection conn = url.openConnection();
   InputStream inStream = conn.getInputStream();
   FileOutputStream fs = new FileOutputStream("c:/abc.gif");

   byte[] buffer = new byte[1204];
   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();
  }
 }

第二种方法：

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();
 }

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