struts 如何获取 file 类型数据

看了STRUTS源代码
怎么也没看到 ActionForm 里面的
MultipartRequestHandler multipartRequestHandler
如何获取到到request的数据的代码

以下为RequestUtils拷贝属性方法,忘大侠们指点一二:

public static void populate(Object bean, String prefix, String suffix,
        HttpServletRequest request)
        throws ServletException {
        // Build a list of relevant request parameters from this request
        HashMap properties = new HashMap();

        // Iterator of parameter names
        Enumeration names = null;

        // Map for multipart parameters
        Map multipartParameters = null;

        String contentType = request.getContentType();
        String method = request.getMethod();
        boolean isMultipart = false;

        if (bean instanceof ActionForm) {
            ((ActionForm) bean).setMultipartRequestHandler(null);
        }

        MultipartRequestHandler multipartHandler = null;
        if ((contentType != null)
            && (contentType.startsWith("multipart/form-data"))
            && (method.equalsIgnoreCase("POST"))) {
            // Get the ActionServletWrapper from the form bean
            ActionServletWrapper servlet;

            if (bean instanceof ActionForm) {
                servlet = ((ActionForm) bean).getServletWrapper();
            } else {
                throw new ServletException("bean that's supposed to be "
                    + "populated from a multipart request is not of type "
                    + "\"org.apache.struts.action.ActionForm\", but type "
                    + "\"" + bean.getClass().getName() + "\"");
            }

            // Obtain a MultipartRequestHandler
            multipartHandler = getMultipartHandler(request);

            if (multipartHandler != null) {
                isMultipart = true;

                // Set servlet and mapping info
                servlet.setServletFor(multipartHandler);
                multipartHandler.setMapping((ActionMapping) request
                    .getAttribute(Globals.MAPPING_KEY));

                // Initialize multipart request class handler
                multipartHandler.handleRequest(request);

                //stop here if the maximum length has been exceeded
                Boolean maxLengthExceeded =
                    (Boolean) request.getAttribute(MultipartRequestHandler.ATTRIBUTE_MAX_LENGTH_EXCEEDED);

                if ((maxLengthExceeded != null)
                    && (maxLengthExceeded.booleanValue())) {
                    ((ActionForm) bean).setMultipartRequestHandler(multipartHandler);
                    return;
                }

                //retrieve form values and put into properties
                multipartParameters =
                    getAllParametersForMultipartRequest(request,
                        multipartHandler);
                names = Collections.enumeration(multipartParameters.keySet());
            }
        }

        if (!isMultipart) {
            names = request.getParameterNames();
        }

        while (names.hasMoreElements()) {
            String name = (String) names.nextElement();
            String stripped = name;

            if (prefix != null) {
                if (!stripped.startsWith(prefix)) {
                    continue;
                }

                stripped = stripped.substring(prefix.length());
            }

            if (suffix != null) {
                if (!stripped.endsWith(suffix)) {
                    continue;
                }

                stripped =
                    stripped.substring(0, stripped.length() - suffix.length());
            }

            Object parameterValue = null;

            if (isMultipart) {
                parameterValue = multipartParameters.get(name);
            } else {
                parameterValue = request.getParameterValues(name);
            }

            // Populate parameters, except "standard" struts attributes
            // such as 'org.apache.struts.action.CANCEL'
            if (!(stripped.startsWith("org.apache.struts."))) {
                properties.put(stripped, parameterValue);
            }
        }

        // Set the corresponding properties of our bean
        try {
            BeanUtils.populate(bean, properties);
        } catch (Exception e) {
            throw new ServletException("BeanUtils.populate", e);
        } finally {
            if (multipartHandler != null) {
                // Set the multipart request handler for our ActionForm.
                // If the bean isn't an ActionForm, an exception would have been
                // thrown earlier, so it's safe to assume that our bean is
                // in fact an ActionForm.
                ((ActionForm) bean).setMultipartRequestHandler(multipartHandler);
            }
        }
    }