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为了简单起见，我有一个带有小表单的 jsp 文件，其中包含 2 个选择选项、一个文件上传选项和一个提交按钮。 servlet 接收值，处理它们(即将文件放入数据库)，然后通过请求属性显示一条消息并重定向回原始 jsp 页面。
我的问题是，当用户尝试从同一 jsp 页面上传另一个文件时，servlet 会接收从先前提交中选择的选择值，而不是新的提交尝试。在 servlet 已经重定向回 jsp 后，同一用户如何上传具有不同选择选项值的另一个文件？
同样，如何清除第一次提交时打印的成功消息，直到再次成功上传？目前，即使用户开始选择要提交的新值后，成功消息仍保留在页面上。
相关代码如下:
JSP文件
<body >
<h3 style="color:red">${msg4}</h3>
<form id="uploadForm" method="post" action="UploadServlet"enctype="multipart/form-data">
<br />
<% UserBean currentUser = (UserBean)(session.getAttribute"currentSessionUser"));%>
Course Number:
<select name="courseNo">
<option value="CS1">CS1</option>
<option value="CS2">CS2</option>
</select>
<br />
Assignment Number:
<select name="hwNo" id="hwNo" >
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
</select>
<br />
Assignment (must be a zip file): <input type="file" name="dataFile" id="fileChooser" /><br />
<br /> <input type="submit" value="Upload" />
</form>
<h3 style="color:red">${msg2}</h3>
</body>
相关Servlet代码
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
HttpSession session = request.getSession(true);
UserBean currentUser = (UserBean)(session.getAttribute("currentSessionUser"));
String uName = currentUser.getUsername();
if (!ServletFileUpload.isMultipartContent(request))
{return;}
DiskFileItemFactory factory = new DiskFileItemFactory();
factory.setSizeThreshold(THRESHOLD_SIZE);
factory.setRepository(new File(System.getProperty("java.io.tmpdir")));
ServletFileUpload upload = new ServletFileUpload(factory);
upload.setFileSizeMax(MAX_FILE_SIZE);
upload.setSizeMax(REQUEST_SIZE);
try
{
List<FileItem> items = new ServletFileUpload(new DiskFileItemFactory()).parseRequest(request);
for (FileItem item : items)
{
if (item.isFormField())
{
String fieldname = item.getFieldName();
if(fieldname.equals("courseNo"))
courseNo = item.getString();
if(fieldname.equals("hwNo"))
{
hwNo = item.getString();
homeworkNo = Integer.parseInt(hwNo);
}
Boolean exists = checkIfHWNoExists(homeworkNo, uName);
if(exists)
{
request.setAttribute("msg4", "You've already made a submission for " +
"assignment number " + homeworkNo +"." +
"<br />If you need to change your submission, " +
"please contact your teacher.");
request.getRequestDispatcher("/upload.jsp").forward(request, response);
return;
}
}
if (!item.isFormField())
{
(item.getName()).getName();
File storeFile = new File(item.getName());
String fileName = storeFile.getName();
if(!fileName.endsWith(".zip"))
{
request.setAttribute("msg", "Must be a zip file! Try again!");
request.getRequestDispatcher("/upload.jsp").forward(request, response);
return;
}
else
{
String mimeType = new MimetypesFileTypeMap().getContentType(storeFile);
//for putting file into database
putFileIntoDB(uName, homeworkNo, fileName, mimeType, storeFile);
request.setAttribute("msg2", "File uploaded successfully!");
request.getRequestDispatcher("/upload.jsp").forward(request, response);
}
}
}
//request.setAttribute("message", "Upload has been done successfully!");
}
catch (Exception ex)
{
request.setAttribute("message", "There was an error: " + ex.getMessage());
}
("/message.jsp").forward(request, response);
}
最佳答案
问题出在 servlet 的循环中。这是更正后的 doPost 方法，完全删除了循环，因为它不是必需的。
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
String courseNo;
int homeworkNo;
HttpSession session = request.getSession(true);
UserBean currentUser = (UserBean)(session.getAttribute("currentSessionUser"));
String uName = currentUser.getUsername();
if (!ServletFileUpload.isMultipartContent(request))
{return;}
try
{
List<FileItem> items = new ServletFileUpload(new DiskFileItemFactory()).parseRequest(request);
courseNo = items.get(0).getString();
homeworkNo = Integer.parseInt(items.get(1).getString());
if(checkIfHWNoExists(courseNo, homeworkNo, uName))
{
request.setAttribute("msg4", "You've already made a submission for Course Number " + courseNo + ", "+
"Assignment number " + homeworkNo +"." +
"<br />If you need to change your submission, " +
"please contact your teacher.");
request.getRequestDispatcher("/upload.jsp").forward(request, response);
return;
}
else//ok to add new HW, it doesn't exist
{
File storeFile = new File(items.get(2).getName());
String fileName = storeFile.getName();
if(!fileName.endsWith(".zip"))
{
request.setAttribute("msg", "Must be a zip file! Try again!");
request.getRequestDispatcher("/upload.jsp").forward(request, response);
return;
}
else
{
String mimeType = new MimetypesFileTypeMap().getContentType(storeFile); //for putting file into database
putFileIntoDB(uName, courseNo, homeworkNo, fileName, mimeType, storeFile);
request.setAttribute("msg2", "File uploaded successfully!");
request.getRequestDispatcher("/upload.jsp").forward(request, response);
}
}
}//try
catch (Exception ex)
{
request.setAttribute("msg", "There was an error: " + ex.getMessage());
request.getRequestDispatcher("/upload.jsp").forward(request, response);
}
}
关于java - 如何在 "re-submit"之后将新的表单参数从 jsp 传递到 servlet？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/14959306/
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