怎么将File转换为MultipartFile类型

package com.xiaojd.test;import java.io.File;import java.io.FileInputStream;import java.io.IOException;import java.io.OutputStream;import org.apache.commons.fileupload.FileItem;import org.apache.commons.fileupload.FileItemFactory;import org.apache.commons.fileupload.disk.DiskFileItemFactory;import org.springframework.web.multipart.MultipartFile;import org.springframework.web.multipart.commons.CommonsMultipartFile;public class Test {public static void main(String[] args) {String picPath ="D://pic//1.png";MultipartFile file = getMulFileByPath(picPath);try {byte[] bytes = file.getBytes();for(byte b : bytes){System.out.print(b);}} catch (IOException e) {e.printStackTrace();}//图片上传picUpload(file);}private static void picUpload(MultipartFile file) {//图片上传 if (file!=null) {// 判断上传的文件是否为空            String path=null;// 文件路径            String type=null;// 文件类型            String fileName=file.getOriginalFilename();// 文件原名称            System.out.println("上传的文件原名称:"+fileName);            // 判断文件类型            type=fileName.indexOf(".")!=-1?fileName.substring(fileName.lastIndexOf(".")+1, fileName.length()):null;            if (type!=null) {// 判断文件类型是否为空                if ("GIF".equals(type.toUpperCase())||"PNG".equals(type.toUpperCase())||"JPG".equals(type.toUpperCase())) {                    // 项目在容器中实际发布运行的根路径//                    String realPath=request.getSession().getServletContext().getRealPath("/");                //哥哥自己写的路径                String realPath="F://pic//";                    // 自定义的文件名称                    String trueFileName=fileName;                    // 设置存放图片文件的路径                    path=realPath+trueFileName;                    System.out.println("存放图片文件的路径:"+path);                    // 转存文件到指定的路径                    try {file.transferTo(new File(path));}  catch (Exception e) {e.printStackTrace();}                    System.out.println("文件成功上传到指定目录下");                }else {                    System.out.println("不是我们想要的文件类型,请按要求重新上传");                }            }else {                System.out.println("文件类型为空");            }        }            System.out.println("没有找到相对应的文件");}private static MultipartFile getMulFileByPath(String picPath) {FileItem fileItem = createFileItem(picPath);MultipartFile mfile = new CommonsMultipartFile(fileItem);return mfile;}private static FileItem createFileItem(String filePath)    {        FileItemFactory factory = new DiskFileItemFactory(16, null);        String textFieldName = "textField";        int num = filePath.lastIndexOf(".");        String extFile = filePath.substring(num);        FileItem item = factory.createItem(textFieldName, "text/plain", true,            "MyFileName" + extFile);        File newfile = new File(filePath);        int bytesRead = 0;        byte[] buffer = new byte[8192];        try        {            FileInputStream fis = new FileInputStream(newfile);            OutputStream os = item.getOutputStream();            while ((bytesRead = fis.read(buffer, 0, 8192))                != -1)            {                os.write(buffer, 0, bytesRead);            }            os.close();            fis.close();        }        catch (IOException e)        {            e.printStackTrace();        }        return item;    }}