如何遍历JSP中的对象列表

Question

Hi friends i am trying iterate through a list that contains list of objects I am trying to iterate through that list . each element of the list is a 'object'. I accessing the variables of that 'object' with the help of c:forEach . I am getting the values. but the same again and again . I dont know if i am doing any mistake while adding objects to list in the servlet or in the jsp while iterating through them.

Here is my servlet code

FileInfo fileInfo = new FileInfo();
            List<FileInfo> fileInfoList = new ArrayList<FileInfo>();

            HashMap<String, String> uploadHistory = new HashMap<String, String>();

            while(rs.next()) {

                fileInfo.setFile_id(rs.getString("file_id"));
                fileInfo.setFile_name(rs.getString("file_name"));
                fileInfo.setUpload_time(rs.getString("upload_time"));
                fileInfo.setUsername(rs.getString("username"));     

                fileInfoList.add(fileInfo);

                uploadHistory.put(rs.getString("file_name"),rs.getString("upload_time"));
            }

            request.setAttribute("uploadHistory",uploadHistory);
            request.setAttribute("fileInfo",fileInfo);
            request.setAttribute("fileInfoList", fileInfoList);
            RequestDispatcher rd = request.getRequestDispatcher("/UploadHistoryJsp");
            rd.forward(request, response);

Here is my jsp

<div class="panel-body">
                    <table id="uploadHistoryTable" class="table">
                        <thead>
                            <tr>
                            <th><strong>File Name</strong></th>
                            <th><strong>Date & Time</strong></th>
                            </tr>
                        </thead>

                        <tbody>

                            <c:forEach var="uploaded" items="${fileInfoList}">
                            <tr>

                                <td><a href="${pageContext.request.contextPath}/DownloadServlet?f=${uploaded.file_name}&p=${uploaded.username}">${uploaded.file_name}</a></td>
                                <td>${uploaded.upload_time}</td>
                            </tr>
                            </c:forEach>
                        </tbody>
                    </table>

                </div>
            </div>
        </div><!-- panel-body -->

Please help . Sorry for any confusion.

Answer 1

Move this line: FileInfo fileInfo = new FileInfo(); within the while loop:

while(rs.next()) {
FileInfo fileInfo = new FileInfo();
....

As is, you are creating only one instance and keep updating the same. Most likely you keep on seeing the last element you are pulling from the database multiple times.

Answer 2

You are adding same object again and again. You need to initiate FileInfo inside while loop

  while(rs.next()) {
     FileInfo fileInfo= new FileInfo();
          .....
     fileInfoList.add(fileInfo)
  }

Answer 3

The problem with your code is you're always updating a single instance of FileInfo through fileInfo variable, so in each iteration you're just overwriting a single object's state.

   FileInfo fileInfo = new FileInfo();
   --------
    while(rs.next()) {
      // updating fileInfo from result set
   }

Move that FileInfo into the while loop like below

   while(rs.next()) {
      FileInfo fileInfo = new FileInfo();
      // update new fileInfo from result set and add to fileInfoList
   }