ServletFileUpload#parseRequest(request) 返回一个空列表 [英] ServletFileUpload#parseRequest(request) returns an empty list

问题描述

我在 Android 中有一个客户端应用程序，它使用 HttpURLConnection 将文件发送到服务器.服务器使用 Apache Commons FileUpload API 来解析表单数据值.

I have a client application in Android which uses HttpURLConnection to send files to the server. The server uses the Apache Commons FileUpload API to parse the form-data values.

HttpURLConnection 发送这个请求:

-----------------------------4912995119421
Content-Disposition: form-data; name="deviceid"

9428103
-----------------------------4912995119421
Content-Disposition: form-data; name="countryid"

598
-----------------------------4912995119421
Content-Disposition: form-data; name="number"

98621360
-----------------------------4912995119421
Content-Disposition: form-data; name="file"; filename="2012-12-08 17.42.18.jpg"
Content-Type: image/jpeg

ÿØÿá1 Exif  II*    
      @      °      ª    
   ²              ¼       Ä   (       1    Ì   2    Ø          i‡    ì   %ˆ      n  SAMSUNG GT-S5360L H      H      S5360LUHLB1 2012:12:08 17:42:18  š‚    î  ?‚    ö  "ˆ       'ˆ    È    ?    0220?    þ  ?      ‘     ’    &  ’       
’    .        0100             @       °       >  £       ¤        ¤        ¤    6  ¤                     
   2012:12:08 17:42:18 2012:12:08 17:42:18    
     d               R98      0100                         (           ¤      T.      ÿØÿà JFIF      ÿÛ C @@ÿÛ 
-----------------------------4912995119421--

服务器代码:

    String contentType = request.getContentType();
    if ((contentType.indexOf("multipart/form-data") == -1)) {
        response.setStatus(HttpServletResponse.SC_NOT_FOUND);
        return;
    }


    long maxFileSize = (2 * 1024 * 1024);

    int maxMemSize = (2 * 1024 * 1024);

    DiskFileItemFactory factory = new DiskFileItemFactory();
    // maximum size that will be stored in memory
    factory.setSizeThreshold(maxMemSize);

    // Create a new file upload handler
    ServletFileUpload upload = new ServletFileUpload(factory);
    // maximum file size to be uploaded.

    upload.setSizeMax(maxFileSize);

    List fileItems = upload.parseRequest(request);
    Iterator i = fileItems.iterator();


    //leo primero todas las variables.

    int deviceID = 0;
    int countryID = 0;
    String phoneNumber = "";



    while (i.hasNext()) {
        FileItem fi = (FileItem) i.next();

        if (fi.isFormField()) {
            String variable = fi.getFieldName();
            if (variable.equals("deviceid")) {
                deviceID = Integer.parseInt(fi.getString());
            } else if (variable.equals("countryid")) {
                countryID = Integer.parseInt(fi.getString());
            } else if (variable.equals("number")) {
                phoneNumber = String.valueOf(Long.parseLong(fi.getString()));
            }

        }

    }

    if (deviceID == 0 || countryID == 0 || phoneNumber.equals("")) {
        response.setStatus(HttpServletResponse.SC_NOT_FOUND);
        return;
    }

问题出在List fileItems = upload.parseRequest(request);这一行.返回的列表为空，我无法获取表单数据值.

The problem is in the line List fileItems = upload.parseRequest(request);. The returned list is empty and I can not get the form-data values.

推荐答案

如果您事先已经(隐式地)解析了请求正文，那么此时它将为空.HTTP 请求正文可以仅被读取/解析一次(因为客户端只发送了一次，不会多次发送).

It will be empty at that point if you have already (implicitly) parsed the request body beforehand. The HTTP request body can be read/parsed only once (as the client has sent it only once and won't send it multiple times).

当您在将请求提供给 Commons FileUpload 之前调用以下任何方法时，请求正文将被隐式读取/解析:

The request body will be implicitly read/parsed when you have invoked any of the following methods before feeding the request to Commons FileUpload:

request.getParameter();
request.getParameterMap();
request.getParameterNames();
request.getParameterValues();
request.getReader();
request.getInputStream();

您需要确保事先不调用任何这些方法(还要检查所有 servlet 过滤器以确保).

You need to make absolutely sure that you are not calling any of those methods beforehand (also check all servlet filters to be sure).

如果您已经确保没有这样做，那么唯一可能的原因是边界标题不正确和/或使用了不正确的换行符(它确实必须是 CR+LF，因此不仅仅是 LF).您可以在 使用 java.net.URLConnection 来触发和处理 HTTP 请求，在上传文件"部分下.

If you've already ensured that you aren't doing that, then the only other possible causes would be an incorrect boundary header and/or using incorrect newlines (it has really to be CR+LF and thus not alone LF). You can find a concrete and proper example at the bottom of Using java.net.URLConnection to fire and handle HTTP requests, under the section "Uploading files".

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