Springboot Http文件的访问 Url 转换 MultipartFile ，File 转 MultipartFile

pom.xml

        <dependency>
            <groupId>commons-fileupload</groupId>
            <artifactId>commons-fileupload</artifactId>
            <version>1.2.2</version>
        </dependency>

MyFileConvertUtil.java

/**
 * @Author: JCccc
 * @Date: 2022-8-25 02:15
 * @Description:
 */
public class MyFileConvertUtil {

    protected static final Logger logger = LoggerFactory.getLogger(MyFileConvertUtil.class);

    /**
     * Url 转换 MultipartFile
     * @param url
     * @param fileName
     * @return
     * @throws Exception
     */
    public static MultipartFile urlToMultipartFile(String url, String fileName) throws Exception {
        logger.info("开始 url 转换 MultipartFile，url={} ,fileName={}",url,fileName);
        File file = null;
        MultipartFile multipartFile = null;
        try {
            HttpURLConnection httpUrl = (HttpURLConnection) new URL(url).openConnection();
            httpUrl.connect();
            logger.info("成功建立httpUrl连接"+httpUrl.toString());
            file = inputStreamToFile(httpUrl.getInputStream(),fileName);
            multipartFile = fileToMultipartFile(file);
            httpUrl.disconnect();
        } catch (Exception e) {
            e.printStackTrace();
        }
        logger.info("完成 url 转换 MultipartFile，url={} ,fileName={}",url,fileName);
        return multipartFile;
    }


    /**
     * InputStream 转 File
     * @param ins
     * @param fileName
     * @return
     * @throws Exception
     */
    public static File inputStreamToFile(InputStream ins, String fileName) throws Exception{
        logger.info("开始 InputStream 转换 File,fileName={}",fileName);
        File file = new File(System.getProperty("java.io.tmpdir") + File.separator + fileName);
        OutputStream os = new FileOutputStream(file);
        int bytesRead;
        int len = 8192;
        byte[] buffer = new byte[len];
        while ((bytesRead = ins.read(buffer, 0, len)) != -1) {
            os.write(buffer, 0, bytesRead);
        }
        os.close();
        ins.close();
        logger.info("完成 InputStream 转换 File,fileName={}",fileName);
        return file;
    }


    /**
     * File 转 MultipartFile
     * @param file
     * @return
     */
    public static CommonsMultipartFile fileToMultipartFile(File file) {
        logger.info("fileToMultipartFile文件转换中："+file.getAbsolutePath());
        FileItemFactory factory = new DiskFileItemFactory(16, null);
        FileItem item=factory.createItem(file.getName(),"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 new CommonsMultipartFile(item);
    }

}

使用简例：
 

    @RequestMapping("/test")
    public void test(@RequestParam String fileUrl)  {
        try {
            File fileAuth = new File(fileUrl);
            //原文件名
            String sourceName = fileAuth.getName();
            //自己起文件名
            String newFileName="JCccc学Java文件名.xlsx";

            MultipartFile file = MyFileConvertUtil.urlToMultipartFile(fileUrl, newFileName);

        } catch (Exception e) {
            e.printStackTrace();
        }
    }