文件上傳過程中，如果我們能看到進(jìn)度條會更好，實(shí)現(xiàn)思路是服務(wù)器端用監(jiān)聽器實(shí)時(shí)監(jiān)聽進(jìn)度并存入session，客戶端異步請求服務(wù)器端獲得上傳進(jìn)度，并進(jìn)行效果渲染。

效果圖：

服務(wù)器端servlet：

public class UploadServlet extends HttpServlet {  @Override  protected void doGet(HttpServletRequest req, HttpServletResponse resp)      throws ServletException, IOException {    //取出監(jiān)聽器MyProgress在session中保存的進(jìn)度信息    String progress=(String) req.getSession().getAttribute("progress");    //響應(yīng)    resp.getWriter().print(progress);    //清除session中保存的數(shù)據(jù)//    req.getSession().removeAttribute("progress");  }  @Override  protected void doPost(HttpServletRequest req, HttpServletResponse resp)      throws ServletException, IOException {    req.setCharacterEncoding("UTF-8");    DiskFileItemFactory factory=new DiskFileItemFactory();    ServletFileUpload upload=new ServletFileUpload(factory);    upload.setProgressListener(new MyProgressListener(req));    try {      List<FileItem> list = upload.parseRequest(req);      for (FileItem fileItem : list) {        if (fileItem.isFormField()) {//普通表單        }else{//上傳文件          String path=req.getRealPath("uploads");          String fileName=fileItem.getName();          File file=new File(path, fileName);          fileItem.write(file);          System.out.println("成功上傳文件："+fileName);        }      }    } catch (Exception e) {      System.out.println("文件上傳發(fā)生錯(cuò)誤！");      e.printStackTrace();    }  }}

服務(wù)器端監(jiān)聽器：

public class MyProgressListener implements ProgressListener {  private HttpSession session;  public MyProgressListener(HttpServletRequest request){    session = request.getSession();  }  @Override  public void update(long pBytesRead, long pContentLength, int pItems) {    //將數(shù)據(jù)進(jìn)行格式化    //已讀取數(shù)據(jù)由字節(jié)轉(zhuǎn)換為M    double readM=pBytesRead/1024.0/1024.0;    //已讀取數(shù)據(jù)由字節(jié)轉(zhuǎn)換為M    double totalM=pContentLength/1024.0/1024.0;    //已讀取百分百    double percent=readM/totalM;        //格式化數(shù)據(jù)    //已讀取    String readf=dataFormat(pBytesRead);    //總大小    String totalf=dataFormat(pContentLength);    //進(jìn)度百分百    NumberFormat format=NumberFormat.getPercentInstance();    String progress=format.format(percent);        //將信息存入session    session.setAttribute("progress", progress);        //打印消息到控制臺    System.out.println("pBytesRead===>"+pBytesRead);    System.out.println("pContentLength==>"+pContentLength);    System.out.println("pItems===>"+pItems);    System.out.println("readf--->"+readf);    System.out.println("totalf--->"+totalf);    System.out.println("progress--->"+progress);  }  /**   * 格式化讀取數(shù)據(jù)的顯示   * @param data要格式化的數(shù)據(jù) 單位byte   * @return 格式化后的數(shù)據(jù)，如果小于1M顯示單位為KB，如果大于1M顯示單位為M   */  public String dataFormat(double data){    String formdata="";    if (data>=1024*1024) {//大于等于1M      formdata=Double.toString(data/1024/1024)+"M";    }else if(data>=1024){//大于等于1KB      formdata=Double.toString(data/1024)+"KB";    }else{//小于1KB      formdata=Double.toString(data)+"byte";    }    return formdata.substring(0, formdata.indexOf(".")+2);  }}