1、 ListFileServlet.java
a) 得到文件保存目錄的真是路徑
b) 創建方法:void listFiles(File file,Map map),迭代處理所有目錄及文件,將所有文件存入Map對象中,K——V uuidname——realname
c) 將Map對象寫入request,傳至listfiles.jsp
- public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
- //得到保存上傳文件的文件夾
- String savepath = this.getServletContext().
- getRealPath("/WEB-INF/upload");
- Map map = new HashMap();
- //迭歸文件夾下面的所有文件 迭歸過程中如何保存迭歸出來的數據
- listFiles(new File(savepath),map);
- request.setAttribute("map", map);
- request.getRequestDispatcher("/listfile.jsp").
- forward(request, response);
- }
- private void listFiles(File file,Map map) {
- if(file.isFile()){
- String uuidname = file.getName();
- String realname = uuidname.
- substring(uuidname.indexOf("_")+1);
- map.put(uuidname, realname);
- }else{
- //得到目錄下所有的文件
- File files[] = file.listFiles();
- for(File f: files){
- listFiles(f,map);
- }
- }
2、 listfiles.jsp
取出map中的數據,並構建url作爲下載鏈接的href屬性值
- <c:forEach var="me" items="${filesMap}">
- <c:url var="fileAddr" value="/servlet/DownloadServlet">
- <c:param name="uuidName">${me.key }</c:param>
- <c:param name="realName">${me.value }</c:param>
- </c:url>
- 文件名:${me.value }<a href="${fileAddr }" >下載</a><br/>
- </c:forEach>
顯示結果如下:
3、 DownloadServlet.java
a) 從request中取出文件名等信息,注意中文字符使用的urlencoding,需要進行手動編碼轉換。
b) 根據文件的uuidName計算出文件的存儲路徑
c) 判斷目標文件是否存在
d) 設置response的header中的content-disposition值爲attachment;filename=realName
e) 獲取輸入流,並寫入輸出流
- public void doGet(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- String uuidName = request.getParameter("uuidName");
- String realName = request.getParameter("realName");
- uuidName = new String(uuidName.getBytes("iso8859-1"),"utf-8");
- //真實文件名取出來必須經過轉碼,然後因爲需要作爲下載鏈接地址,所以需要再一次轉碼
- realName = URLEncoder.encode(new String(realName.getBytes("iso8859-1"),"utf-8"),"utf-8");
- System.out.println(getFileAddr(uuidName));
- File file = new File(getFileAddr(uuidName));
- if(!file.exists()){
- request.setAttribute("message", "下載的文件不存在!");
- request.getRequestDispatcher("/message.jsp")
- .forward(request, response);
- }else{
- response.setHeader("content-disposition", "attachment;filename="+realName);
- FileInputStream fin = new FileInputStream(file);
- OutputStream out = response.getOutputStream();
- byte[] buffer = new byte[1024];
- int len = 0;
- while((len = fin.read(buffer))>0){
- out.write(buffer,0,len);
- }
- fin.close();
- }
- }
- public String getFileAddr(String uuidName){
- int dir1 = uuidName.hashCode() & 0xf;
- int dir2 = (uuidName.hashCode()>>4) & 0xf;
- String fileAddr = this.getServletContext().getRealPath("/WEB-INF/upload")
- +"\\"+ dir1+"\\" + dir2 +"\\" + uuidName;
- return fileAddr;
- }