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;
    }

}