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");
 } 
 }

总结

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