SpringMVC中servletFileUpload.parseRequest(request)解析爲空獲取不到數據問題

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1. 緣由分析
2. 解決方案

緣由分析

首先咱們來看下Spring mvc 中文件上傳的配置

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

        <property name="maxUploadSize" value="2000000000" />
    </bean>

再來看看Controller中使用

public void upload2(HttpServletRequest request) {
        // 轉型爲MultipartHttpRequest
        try {
            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";
    }

這裏springMVC 都爲咱們封裝好成本身的文件對象了,轉換的過程就在咱們所配置的CommonsMultipartResolver這個轉換器裏面下面再來看看它的源碼

他的轉換器裏面就是調用common-fileupload的方式解析,而後再使用parseFileItems()方法封裝成本身的文件對象 . 

 

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

你們應該發現了上面的這句代碼,已經使用過fileUpload解析過request了,你在Controller裏面接收到的request都已是解 析過的,你再次使用upload進行解析獲取到的確定是空,這個就是問題的所在(你們能夠在servlet裏面實驗,看看第二次解析後能不能獲取到數據, 固然是不能的)

解決方案

1)刪除Spring MVC文件上傳配置

 

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

        <property name="maxUploadSize" value="2000000000" />
    </bean>
     -->

在控制器裏面本身完成request的解析(固然上面spring MVC提供的兩種方法是不能用的,全部上傳的地方都須要本身作處理)

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)若是是須要使用的ProgressListener監聽器咱們能夠重寫 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 {
    @Override
    protected 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);
        }
    }
}

監聽器方法

import org.apache.commons.fileupload.ProgressListener;

public class FileUploadListener implements ProgressListener {

    @Override
    public void update(long arg0, long arg1, int arg2) {
        //arg0 已經上傳多少字節
        //arg1 一共多少字節
        //arg2 正在上傳第幾個文件
        System.out.println(arg0 +"\t" + arg1 +"\t" + arg2);
    }

}

配置文件改成咱們本身的(這種方式的缺陷是,全部文件上傳都須要使用到Listener)

 

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

注: 綜上所述,若是隻是普通的文件上傳spring MVC 徹底能夠完成,若是須要使用進度條的listener前段能夠使用假的進度條或者是上面的兩種方式.