javaweb上传下载实例完整版解析(下)_Java教程

一.显示下载的文件资源

　　要将Web应用系统中的文件资源提供给用户进行下载，首先我们要有一个页面列出上传文件目录下的所有文件，当用户点击文件下载超链接时就进行下载操作，编写一个ListFileServlet，用于列出Web应用系统中所有下载文件。

1.1 文件下载页面
download.html代码如下:

				?

									<!DOCTYPE HTML>

									<html>

									<head>

									   <title>下载文件显示页面</title>

									</head>

									<body>

									  <div id="fileName"></div>

									</body>

									<script >

									$(function(){

									  download();

									}); 

									function download(){ 

									  $.ajax({

									      url: 'cloud/load/download', 

									      type: 'POST',  

									      dataType:'JSON',

									      cache: false, 

									      processData: false, 

									      contentType: false,

									      success : function(date){

									       var file="";

									       $.each(date,function(key,values){

									        var newKey = "/D:/Download/"+key;

									        file += "<div>"+key+"&nbsp;&nbsp;"+"<a href='cloud/load/downloadFile?fileName="+key+"'>"+"下载"+"</a>"+"</div>"+"<br>";

									        $(values).each(function(){

									         file+="\t"+this; 

									        }); 

									       });

									       alert("success"); 

									   }, 

									   error : function(e){

									    alert("error");

									   }

									   });

									 }

									</script>

									</html>

1.2 controller

				?

									@RequestMapping(value = "/download", method = RequestMethod.POST)

									@ResponseBody

									  public Map<String,String> download(HttpServletRequest request, HttpServletResponse response, ModelMap model) throws ServletException, IOException{

									  Map<String,String> map = fileLoadService.doGet(request, response);

									  return map;

									}

1.3 service

				?

									/**

									  * 文件下载显示

									  * @ClassName: FileLoadServiceImpl

									  * @throws IOException 

									  * @throws ServletException 

									  */

									 @Override

									public Map<String,String> doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{

									  //获取上传文件的目录

									  String uploadFilePath = "/D:/Download/";

									  //存储要下载的文件名

									  Map<String,String> fileNameMap = new HashMap<String,String>();

									  //递归遍历filepath目录下的所有文件和目录，将文件的文件名存储到map集合中

									  listfile(new File(uploadFilePath),fileNameMap);

									  return fileNameMap;

									 }  

									public void listfile(File file,Map<String,String> map){

									  //如果file代表的不是一个文件，而是一个目录

									  if(!file.isFile()){

									    //列出该目录下的所有文件和目录

									    File files[] = file.listFiles();

									    //遍历files[]数组

									    for(File f : files){

									    //递归

									     listfile(f,map);

									   }

									   }else{

									     String realName = file.getName().substring(file.getName().indexOf("_")+1);

									     //file.getName()得到的是文件的原始名称，这个名称是唯一的，因此可以作为key，realName是处理过后的名称，有可能会重复

									     map.put(file.getName(), realName);

									   }

									}

									public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

									    doGet(request, response);

									}

二.下载显示的文件资源

2.1 controller

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									@RequestMapping(value = "/downloadFile", method = RequestMethod.GET)

									@ResponseBody

									public void downloadFile(HttpServletRequest request, HttpServletResponse response, ModelMap model) throws ServletException, IOException{

									    String filename =request.getParameter("fileName");

									    fileLoadService.doGetFile(request, response ,filename);

									  }

2.2 service

				?

									   /**

									   * 下载文件到本地 start

									   */

									  @Override

									  public void doGetFile(HttpServletRequest request, HttpServletResponse response,String filename) throws ServletException,IOException {

									  //得到要下载的文件名

									   String fileName = filename;

									   fileName = new String(fileName.getBytes("iso8859-1"),"UTF-8");

									   String fileSaveRootPath="/D:/Download";

									   File file = new File(fileSaveRootPath + "/" + fileName);

									   //如果文件不存在

									   if(!file.exists()){

									     request.setAttribute("message", "您要下载的资源已被删除！！");

									     return;

									   }

									   //处理文件名

									   String realname = fileName.substring(fileName.indexOf("_")+1);

									   //设置响应头，控制浏览器下载该文件

									   response.setHeader("content-disposition", "attachment;filename=" + URLEncoder.encode(realname, "UTF-8"));

									  InputStream fis = new BufferedInputStream(new FileInputStream(fileSaveRootPath + "\\" + fileName));

									  byte[] buffer = new byte[fis.available()]; 

									  fis.read(buffer); //读取文件流

									  fis.close();

									  response.reset(); //重置结果集

									  response.setHeader("content-disposition", "attachment;filename=" + URLEncoder.encode(realname, "UTF-8"));

									  response.addHeader("Content-Length", "" + file.length()); //返回头 文件大小

									  response.setContentType("application/octet-stream");  //设置数据种类 

									  OutputStream os = new BufferedOutputStream(response.getOutputStream()); 

									  os.write(buffer); // 输出文件

									  os.flush();

									  os.close();

									  }

									public void doPostFile(HttpServletRequest request, HttpServletResponse response,String filename)throws ServletException, IOException {

									    doGetFile(request, response,filename);

									}