文件上传“multipart/form”异常 org.apache.commons.fileupload.FileUploadBase$InvalidContentTypeException

我尝试使用 Apache Commons 进行文件上传，但抛出以下异常

org.apache.commons.fileupload.FileUploadBase$InvalidContentTypeException：请求不包含 multipart/form-data 或 multipart/mixed 流，内容类型标头为 null

我的html代码是

<form  name="inp" action="upload.jsp"  method="get" onsubmit="return valid();" enctype="multipart/form-data">
<table align="center" cellspacing="2">

  <tr><td><font size="5" color="#E41B17">Select File</font> </td>
<td><input type="file" name="infile"></td>
</tr>
<tr><td><font size="5" color="#E41B17">Target File Name</font></td>
<td><input type="text" size="20" name="filename"></input></td>
</tr>
<tr></tr>
<tr><td colspan="2" align="center"><input type=submit value="Upload"  ></td></tr>
</table>
<br></br>
<center>
<a href="index.html"><font color="#E41B17">HOME</font></a>
</center>
</form>

我的JSP代码是

   <% 
   String user = (String)session.getAttribute("uname");
   String f = request.getParameter("filename");

   DiskFileUpload upload = new DiskFileUpload();         
   boolean isMultipart=upload.isMultipartContent(request);


   upload.setSizeMax(1048576);     
   List items = upload.parseRequest(request);  
   FileItem  file = (FileItem) items.get(0); 

   String source = file.getName();
      String delim="\\";
   String str="";
   File propfile=new File("C:\\eclipse_practise\\fileupload\\WebContent\\path.properties");

   BufferedInputStream propbuf=new BufferedInputStream(new FileInputStream(propfile));

   Properties path=new Properties();

   path.load(propbuf);

   String serverlocation=path.getProperty("Server_path");

   session.setAttribute("storelocation",serverlocation);

   StringTokenizer st = new StringTokenizer(source,delim);

   while(st.hasMoreTokens())
   {                        
       str=st.nextToken();
   }

   FileItem  name = (FileItem) items.get(1);

   String  target = name.getString();

   File outfile = new File(serverlocation+target);

    file.write(outfile); 

      session.setAttribute("filename",target);

   %>

表单必须是 method="POST"