SpringMVC中servletFileUpload.parseRequest(request)解析为空获取不到数据问题

原因分析

首先我们来看下Spring mvc 中文件上传的配置

<bean id="multipartResolver"class="org.springframework.web.multipart.commons.CommonsMultipartResolver"><property name="defaultEncoding" value="UTF-8" /><property name="maxUploadSize" value="2000000000" /></bean>

再来看看Controller中使用

public void upload2(HttpServletRequest request) {// 转型为MultipartHttpRequesttry {MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) request;List<MultipartFile> fileList = multipartRequest.getFiles("file");for (MultipartFile mf : fileList) {if(!mf.isEmpty()){}}} catch (Exception e) {e.printStackTrace();}}

方式二

public String upload(HttpServletRequest request,@RequestParam(value = "file") MultipartFile[] files) {try {for (MultipartFile mf : files) {if(!mf.isEmpty()){}}} catch (Exception e) {e.printStackTrace();}return "upload";}

这里springMVC 都为我们封装好成自己的文件对象了,转换的过程就在我们所配置的CommonsMultipartResolver这个转换器里面下面再来看看它的源码

他的转换器里面就是调用common-fileupload的方式解析,然后再使用parseFileItems()方法封装成自己的文件对象 . 

List<FileItem> fileItems = ((ServletFileUpload) fileUpload).parseRequest(request);

大家应该发现了上面的这句代码,已经使用过fileUpload解析过request了,你在Controller里面接收到的request都已经是解析过的,你再次使用upload进行解析获取到的肯定是空,这个就是问题的所在(大家可以在servlet里面实验,看看第二次解析后能不能获取到数据,当然是不能的)

解决方案

1)删除Spring MVC文件上传配置

<!-- <bean id="multipartResolver"class="org.springframework.web.multipart.commons.CommonsMultipartResolver"><property name="defaultEncoding" value="UTF-8" /><property name="maxUploadSize" value="2000000000" /></bean> -->

在控制器里面自己完成request的解析(当然上面spring MVC提供的两种方法是不能用的,所有上传的地方都需要自己做处理)

public void upload3(HttpServletRequest request) {DiskFileItemFactory factory = new DiskFileItemFactory();ServletFileUpload upload = new ServletFileUpload(factory);try {List<FileItem> list = upload.parseRequest(request);for(FileItem item : list){if(item.isFormField()){}else{//item.write(new File(""));}}} catch (FileUploadException e) {e.printStackTrace();}}

2)如果是需要使用的ProgressListener监听器我们可以重写 CommonsMultipartResolver的parseRequest方法

package com.lwp.spring.ext;import java.util.List;import javax.servlet.http.HttpServletRequest;import org.apache.commons.fileupload.FileItem;import org.apache.commons.fileupload.FileUpload;import org.apache.commons.fileupload.FileUploadBase;import org.apache.commons.fileupload.FileUploadException;import org.apache.commons.fileupload.servlet.ServletFileUpload;import org.springframework.web.multipart.MaxUploadSizeExceededException;import org.springframework.web.multipart.MultipartException;import org.springframework.web.multipart.commons.CommonsMultipartResolver;import com.lwp.listener.FileUploadListener;public class CommonsMultipartResolverExt extends CommonsMultipartResolver {@Overrideprotected MultipartParsingResult parseRequest(HttpServletRequest request)throws MultipartException {FileUploadListener listener = new FileUploadListener();String encoding = determineEncoding(request);FileUpload fileUpload = prepareFileUpload(encoding);fileUpload.setProgressListener(listener);try {List<FileItem> fileItems = ((ServletFileUpload) fileUpload).parseRequest(request);return parseFileItems(fileItems, encoding);}catch (FileUploadBase.SizeLimitExceededException ex) {throw new MaxUploadSizeExceededException(fileUpload.getSizeMax(), ex);}catch (FileUploadException ex) {throw new MultipartException("Could not parse multipart servlet request", ex);}}}

监听器方法

import org.apache.commons.fileupload.ProgressListener;public class FileUploadListener implements ProgressListener {@Overridepublic void update(long arg0, long arg1, int arg2) {//arg0 已经上传多少字节//arg1 一共多少字节//arg2 正在上传第几个文件System.out.println(arg0 +"\t" + arg1 +"\t" + arg2);}}

配置文件改为我们自己的(这种方式的缺陷是,所有文件上传都需要使用到Listener)

<bean id="multipartResolver"class="com.lwp.spring.ext.CommonsMultipartResolverExt"><property name="defaultEncoding" value="UTF-8" /><property name="maxUploadSize" value="2000000000" /></bean>

注: 综上所述,如果只是普通的文件上传spring MVC 完全可以完成,如果需要使用进度条的listener前段可以使用假的进度条或者是上面的两种方式.