不知道如何迭代<forEach>中提供的“项目”

Question

我的代码对于删除按钮运行良好，但是单击下载按钮时出现错误：

  

错误：-不知道如何遍历

中提供的“项目”

<table id="myInput" style="width:100%;float:left">
  <thead>
  <tr>
  <th>Book Name</th>
  <th>Author</th>
  <th>Course</th>
  <th>Download</th>
  <th>Delete</th>
  </tr>
  </thead>
  <tbody>
  <c:forEach items="${book}" var="approval">  
    <tr>
      <center><td>${approval.bookName}</td></center>
      <center><td>${approval.authorName}</td></center> 
      <center><td>${approval.courseName}</td></center>
      <td> 
        <form action="downloadBook" method="GET">
          <input type="hidden" value="${approval.bookName}" name="bname2"/>
          <input type="submit" value="Download">
        </form>
      </td>
      <td>
        <form action="deleteBook" method="POST">
          <input type="hidden" value="${approval.bookName}" name="bname"/>
          <input type="hidden" value="${approval.courseName}" name="cname"/>
          <input type="submit" value="Delete">
        </form>
      </td>        
    </tr>   
  </c:forEach>
  </tbody>
</table>