ServletFileUpload #parseRequest(request)返回一个空列表

Question

我在Android中有一个客户端应用程序,HttpURLConnection用于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.

该HttpURLConnection发送该请求:

-----------------------------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

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-----------------------------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;
    }

问题就在于此List fileItems = upload.parseRequest(request);.返回的列表为空,我无法获取表单数据值.

Answer 1

如果您已经(隐式)预先解析了请求主体,那么它将是空的.HTTP请求主体只能被读取/解析一次(因为客户端只发送一次并且不会多次发送它).

在将请求提交给Commons FileUpload 之前调用以下任何方法时,将隐式读取/解析请求体:

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

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

如果你已经确定你没有这样做,那么唯一的其他可能原因是不正确的边界标题和/或使用不正确的换行符(它实际上是CR + LF,因此不是单独的LF).您可以在" 使用java.net.URLConnection"的底部找到一个具体而恰当的示例来触发和处理HTTP请求,在"上载文件"部分下.

Answer 2

如果使用spring，检查是否有<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver" />in xml文件。有一个功能

protected HttpServletRequest checkMultipart(HttpServletRequest request) throws MultipartException {
        if (this.multipartResolver != null && this.multipartResolver.isMultipart(request)) {
            if (request instanceof MultipartHttpServletRequest) {
                logger.debug("Request is already a MultipartHttpServletRequest - if not in a forward, " +
                        "this typically results from an additional MultipartFilter in web.xml");
            }
            else {
                return this.multipartResolver.resolveMultipart(request);
            }
        }
        // If not returned before: return original request.
        return request;
    }

“吃”多部分项目。它会导致三个小时的疼痛。