第一種方法：

public HttpServletResponse download(String path,HttpServletResponse response) {
  try {
   // path是指欲下載的檔案的路徑。
   File file = new File(path);
   // 取得檔名。
   String filename = file.getName();
   // 取得檔案的字尾名。
   String ext = filename.substring(filename.lastIndexOf(".") + 1).toUpperCase();

   // 以流的形式下載檔案。
   InputStream fis = new BufferedInputStream(new FileInputStream(path));
   byte[] buffer = new byte[fis.available()];
   fis.read(buffer);
   fis.close();
   // 清空response
   response.reset();
   // 設定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 {
  // 下載本地檔案
  String fileName = "Operator.doc".toString(); // 檔案的預設儲存名
  // 讀到流中
  InputStream inStream = new FileInputStream("c:/Operator.doc");// 檔案的存放路徑
  // 設定輸出的格式
  response.reset();
  response.setContentType("bin");
  response.addHeader("Content-Disposition","attachment; filename=\"" + fileName + "\"");
  // 迴圈取出流中的資料
  byte[] b = new byte[100];
  int len;
  try {
   while ((len = inStream.read(b)) > 0)
    response.getOutputStream().write(b,len);
   inStream.close();
  } catch (IOException e) {
   e.printStackTrace();
  }
 }

 public void downloadNet(HttpServletResponse response) throws MalformedURLException {
  // 下載網路檔案
  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,byteread);
   }
  } catch (FileNotFoundException e) {
   e.printStackTrace();
  } catch (IOException e) {
   e.printStackTrace();
  }
 }

第二種方法：

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) { // 線上開啟方式
   URL u = new URL("file:///" + filePath);
   response.setContentType(u.openConnection().getContentType());
   response.setHeader("Content-Disposition","inline; filename=" + f.getName());
   // 檔名應該編碼成UTF-8
  } else { // 純下載方式
   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,len);
  br.close();
  out.close();
 }

以上就是JAVA實現下載檔案功能的兩種方法的詳細內容，更多關於JAVA實現下載檔案的資料請關注我們其它相關文章！