protected void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    // 1.獲取下載目標
    String filename = request.getParameter("target");
    System.out.println(filename);
    // 2.找到下載目標
    String path = getServletContext().getRealPath("download/" + filename);
    File file = new File(path);
    if (file.exists()) {
      // 3.如果文件存在，那么設置響應的內容為下載，告訴瀏覽器將信息識別成下載
      // 判斷一下瀏覽器
      String agent = request.getHeader("User-Agent");
      if (agent.contains("Firefox")) {// 火狐
        BASE64Encoder base64Encoder = new BASE64Encoder();
        filename = "=?utf-8?B?" + base64Encoder.encode(filename.getBytes("utf-8")) + "?=";
      } else {// ie和谷歌
        filename = URLEncoder.encode(filename, "utf-8");
      }
      response.setHeader("Content-Disposition", "attachment; filename=" + filename);
      // 4.獲取文件流
      FileInputStream fis = new FileInputStream(file);
      OutputStream os = response.getOutputStream();
      // 5.返回給瀏覽器
      int len = 0;
      byte[] buffer = new byte[1024];
      while ((len = fis.read(buffer)) != -1) {
        os.write(buffer, 0, len);
      }
      os.flush();// flush一下，確保一下
      os.close();
      fis.close();
    } else {
      response.setContentType("text/html;charset=UTF-8");
      response.getWriter().write("找不到文件");
    }

  }

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    request.setCharacterEncoding("utf-8");
    DiskFileItemFactory factory=new DiskFileItemFactory();//1.創(chuàng)建DiskFileItemFactory工廠類
    ServletFileUpload upload=new ServletFileUpload(factory);//2.創(chuàng)建解析類，用于解析resquest
    try {
      List<FileItem> list = upload.parseRequest(request);//3.解析內容，獲取一個list，數據都存儲在list中
      for(FileItem item:list) {
        if(item.isFormField()) {//判斷是否是普通的表單內容
          System.out.println(item.getFieldName());//獲取的是表單中name屬性的值
          System.out.println(item.getString());//獲取的是對應的表單的值
        }else {//為假，說明是上傳項
          //獲取流，進行處理
          InputStream ism = item.getInputStream();
          String path=getServletContext().getRealPath("/upload/");
          System.out.println(path);
          String filename = item.getName();//這里getName可以獲取文件名
          System.out.println(filename);
          File file=new File(path+filename);
          file.createNewFile();//這里不做文件存在性和名字重復判斷
          OutputStream fos = new FileOutputStream(file);
          //這里直接借助commons.io來做io對接，不然需要做流的讀取和寫入
          IOUtils.copy(ism,fos);//把輸入流的數據拷貝到輸出流
          IOUtils.closeQuietly(ism);
          IOUtils.closeQuietly(fos);
          
        }
      }
    } catch (FileUploadException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
    
    
  }