Controller中servletFileUpload.parseRequest(request)解析为空

缘由分析

首先咱们来看下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";
	}

这里springMVC 都为咱们封装好成本身的文件对象了,转换的过程就在咱们所配置的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,而后再使用parseFileItems()方法封装成本身的文件对象 . 

 

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

你们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都已是解析过的,你再次使用upload进行解析获取到的确定是空,这个就是问题的所在(你们能够在servlet里面实验,看看第二次解析后能不能获取到数据,固然是不能的)

 

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>  
     -->

在控制器里面本身完成request的解析(固然上面spring MVC提供的两种方法是不能用的,全部上传的地方都须要本身作处理)

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)若是是须要使用的ProgressListener监听器咱们能够重写 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 {  
    @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);  
        }  
    }  
}

监听器方法  

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);  
     }   
}

配置文件改成咱们本身的(这种方式的缺陷是,全部文件上传都须要使用到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,若是只是普通的文件上传spring MVC 彻底能够完成,若是须要使用进度条的listener前段能够使用假的进度条或者是上面的两种方式.