Java下载文件的4种方式总结

1.以流的方式下载.

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.下载本地文件

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();
 }
 }

3.下载网络文件

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();
  }
 }

4.支持在线打开的方式

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();
 }

JAVA中批量下载文件，将下载多个文件打包成zip文件下载。

 //批量文件下载(将多个文件打包成zip包下载)
 public static void batchDownLoadFile(HttpServletRequest request,HttpServletResponse response,String filename,String[] filepath,String[] documentname,String loginname){ 
 byte[] buffer = new byte[1024];
 Date date=new Date();
 //生成zip文件存放位置
 String strZipPath = Constant.exportAddress +loginname+date.getTime()+".zip";
 File file=new File(Constant.exportAddress);
 if(!file.isDirectory() && !file.exists()){
 //创建单层目录
 // f.mkdir();
 // 创建多层目录
 file.mkdirs();
 }
 try { 
 ZipOutputStream out = new ZipOutputStream(new FileOutputStream(strZipPath)); 
 // 需要同时下载的多个文件
 for (int i = 0; i < filepath.length; i++) {
 File f=new File(filepath[i]);
 FileInputStream fis = new FileInputStream(f);
 System.out.println(documentname[i]);
 out.putNextEntry(new ZipEntry(documentname[i])); 
 //设置压缩文件内的字符编码，不然会变成乱码 
 out.setEncoding("GBK"); 
 int len; 
 // 读入需要下载的文件的内容，打包到zip文件 
 while ((len = fis.read(buffer)) > 0) { 
 out.write(buffer, 0, len); 
 } 
 out.closeEntry(); 
 fis.close(); 
 } 
 out.close(); 
 PublicMethod.downLoadFile(request, response, strZipPath, filename+".zip");
 File temp=new File(strZipPath);
 if(temp.exists()){
 temp.delete();
 }
 } catch (Exception e) { 
 System.out.println("文件下载错误");
 } 
 }