anchor.diff:      }
   
       function downall() {
  -        window.open("${basePath }downAllFile", "_blank");
  +
  +        // make a check if file list empty, just pop up an alert
  +        var flag = false;
  +        flag = ${noFileFlag} ;
  +
  +        if ( flag !== true  ){
  +            window.open("${basePath }downAllFile", "_blank");
  +        } else {
  +            alert("本科目没有作业提交。");
  +        }
  +
       }
   
       function view(hid) {
  
positive.code:             <td>文件大小</td>
              <td>操作</td>
          </tr>
          <c:forEach items="${fileListByHoid }" var="filelist">
              <tr <c:if test="${filelist.uptime==null}">class='danger'</c:if>>
                  <td><p>${filelist.osubject }</p></td>
                  <td><p>${filelist.oname }</p></td>
                  <td><p>${filelist.uptime==null?"未上传":"已上传" }</p></td>
  
negative.code:     String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + path + "/";
      application.setAttribute("basePath", basePath);
  %>
  <button type="button" class="btn btn-success" style="margin-bottom: 10px;" onclick="downall()">下载全部本科目作业</button>
  <span id="total"></span>
  <div class="table-responsive">
      <table class="table table-hover">
  