Java 将File转换为MultipartFile类型

　　首先转换时需要用到commons-fileupload-1.3.2.jar包，若项目中没有就先加入jar包，实现代码如下：

　　1、根据File创建FileItem

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; /*创建FileItem*/private FileItem createFileItem(File file, String fieldName) {FileItemFactory factory = new DiskFileItemFactory(16, null);FileItem item = factory.createItem(fieldName, "text/plain", true, file.getName());int bytesRead = 0;byte[] buffer = new byte[8192];try {FileInputStream fis = new FileInputStream(file);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;}

byte数组转multipartfile，　　2、通过FileItem对象可以轻松获得CommonsMultipartFile对象，转换成MultiPartFile对象即可使用。

MultipartFile mfile = new CommonsMultipartFile(fileItem);