上一个问题误点了已采纳。。。

就是以前案例里讲过的一个封装了文件上传的工具类

package com.bookshop.global;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

import javax.servlet.http.HttpServletRequest;
import java.io.*;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.UUID;

public class FileUpLoadUitl {
    private static FileUpLoadUitl fileUpLoadUitl;
    private FileUpLoadUitl(){

    }
    public FileUpLoadUitl getInstance(){
        if(fileUpLoadUitl==null){
            fileUpLoadUitl=new FileUpLoadUitl();
        }
        return fileUpLoadUitl;
    }


    /**
     * 修改文件名为唯一文件名，防止上传文件重名
     * @param fileName 上传文件名
     * @return
     */
    private static String getUUIDFileName(String fileName){
        int index=fileName.lastIndexOf(".");
        String extension=fileName.substring(index);
        String uuidFileName= UUID.randomUUID().toString().replace("-","")+extension;
        return uuidFileName;
    }

    /**
     * 文件上传工具
     */
    public static Map fileUpload(HttpServletRequest request){
        Map<String,String > map=new HashMap<String ,String >();
        DiskFileItemFactory diskFileItemFactory=new DiskFileItemFactory();
        ServletFileUpload servletFileUpload=new ServletFileUpload(diskFileItemFactory);
        String url=null;
        String uuidFileName=null;
        try {
            List<FileItem> fileItemList=servletFileUpload.parseRequest(request);
            for(FileItem fileItem:fileItemList){
                //普通项
                if (fileItem.isFormField()){
                    String name=fileItem.getFieldName();
                    String value=fileItem.getString("UTF-8");
                    map.put(name,value);
                }
                //文件上传项
                else{
                    String fileName=fileItem.getName();
                    uuidFileName=getUUIDFileName(fileName);
                    InputStream is=fileItem.getInputStream();
                    String path=request.getServletContext().getRealPath("img");
                    url=path+"\\"+uuidFileName;
                    OutputStream os=new FileOutputStream(url);
                    int length=0;
                    byte[] b=new byte[1024];
                    while((length=is.read(b))!=-1){
                        os.write(b,0,length);
                    }
                    is.close();
                    os.close();
                    map.put("coverPath",request.getContextPath()+"/img/"+uuidFileName);
                }
            }
        } catch (FileUploadException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return map;

    }


}