java 将file转为MultipartFile

可以使用`CommonsMultipartFile`类将`File`对象转换为`MultipartFile`对象。具体步骤如下：

1.导入`commons-fileupload`和`commons-io`依赖：

<dependency>
    <groupId>commons-fileupload</groupId>
    <artifactId>commons-fileupload</artifactId>
    <version>1.4</version>
</dependency>
<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.11.0</version>
</dependency>

2.使用`CommonsMultipartFile`类将`File`对象转换为`MultipartFile`对象：

import org.apache.commons.fileupload.disk.DiskFileItem;
import org.apache.commons.io.FileUtils;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.multipart.commons.CommonsMultipartFile;

import java.io.File;
import java.io.IOException;

public class FileUtil {
    public static MultipartFile fileToMultipartFile(File file) throws IOException {
        DiskFileItem fileItem = new DiskFileItem("file", FileUtils.getFile(file.getPath()).getContentType(), false, file.getName(), (int) file.length(), file.getParentFile());
        fileItem.getOutputStream();
        return new CommonsMultipartFile(fileItem);
    }
}

3.调用`fileToMultipartFile`方法将`File`对象转换为`MultipartFile`对象：

File file = new File("path/to/file");
MultipartFile multipartFile = FileUtil.fileToMultipartFile(file);