基于fileUpload文件上传带进度条效果的实例(必看)

文件上传过程中，如果我们能看到进度条会更好，实现思路是服务器端用监听器实时监听进度并存入session，客户端异步请求服务器端获得上传进度，并进行效果渲染。

效果图：

服务器端servlet：

public class UploadServlet extends HttpServlet {  @Override  protected void doGet(HttpServletRequest req, HttpServletResponse resp)      throws ServletException, IOException {    //取出监听器MyProgress在session中保存的进度信息    String progress=(String) req.getSession().getAttribute("progress");    //响应    resp.getWriter().print(progress);    //清除session中保存的数据//    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()) {//普通表单        }else{//上传文件          String path=req.getRealPath("uploads");          String fileName=fileItem.getName();          File file=new File(path, fileName);          fileItem.write(file);          System.out.println("成功上传文件："+fileName);        }      }    } catch (Exception e) {      System.out.println("文件上传发生错误！");      e.printStackTrace();    }  }}

服务器端监听器：

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) {    //将数据进行格式化    //已读取数据由字节转换为M    double readM=pBytesRead/1024.0/1024.0;    //已读取数据由字节转换为M    double totalM=pContentLength/1024.0/1024.0;    //已读取百分百    double percent=readM/totalM;        //格式化数据    //已读取    String readf=dataFormat(pBytesRead);    //总大小    String totalf=dataFormat(pContentLength);    //进度百分百    NumberFormat format=NumberFormat.getPercentInstance();    String progress=format.format(percent);        //将信息存入session    session.setAttribute("progress", progress);        //打印消息到控制台    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);  }  /**   * 格式化读取数据的显示   * @param data要格式化的数据 单位byte   * @return 格式化后的数据，如果小于1M显示单位为KB，如果大于1M显示单位为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);  }}