Controller中servletFileUpload.parseRequest(request)解析爲空

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.