java将File转换成MultipartFile

青旅半醒 2021-05-20 14:12 853阅读 0赞

项目中遇到将网络图片下载到本地，然后加入签章后再上传到文件服务器。由于下载后的文件是File类型，上传接口接受的是MultipartFile类型，于是需要将File转换成MultipartFile。  
1.引入commons-fileupload的jar

<dependency>
                <groupId>commons-fileupload</groupId>
                <artifactId>commons-fileupload</artifactId>
                <version>1.3.2</version>
    </dependency>

2.定义将文件转换成FileItem的方法

import org.apache.commons.io.FilenameUtils;
    import org.apache.commons.fileupload.FileItem;
    import org.apache.commons.fileupload.FileItemFactory;
    import org.apache.commons.fileupload.disk.DiskFileItemFactory;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Component;
    import org.springframework.web.multipart.MultipartFile;
    import org.springframework.web.multipart.commons.CommonsMultipartFile;
    
      /**
         * 将file转换成fileItem
         * @param file
         * @param fieldName
         * @return
         */
        private FileItem  getMultipartFile(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;
        }

3.调用

File file = new File("C://");          
     FileItem fileItem = this.getMultipartFile(file,"templFileItem");
     MultipartFile multipartFile = new CommonsMultipartFile(fileItem);