文件流转MultipartFile，不使用MockMultipartFile的方式

MockMultipartFile 是一个用于测试的模拟类，通常在单元测试或集成测试中模拟 MultipartFile 的行为。它属于 Spring 框架的测试包 org.springframework.mock.web 中的一部分，不应该在生产环境中使用。

因此我们采用实现MultipartFile接口类的方式，自己实现转换逻辑。

首先创建CustomMultipartFile类

具体代码如下：

import org.apache.commons.io.IOUtils;
import org.springframework.core.io.FileSystemResource;
import org.springframework.web.multipart.MultipartFile;import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;public class CustomMultipartFile implements MultipartFile {private final String name;private final String originalFilename;private final String contentType;private final File file;public CustomMultipartFile(String name, String originalFilename, String contentType, File file) {this.name = name;this.originalFilename = originalFilename;this.contentType = contentType;this.file = file;}@Overridepublic String getName() {return this.name;}@Overridepublic String getOriginalFilename() {return this.originalFilename;}@Overridepublic String getContentType() {return this.contentType;}@Overridepublic boolean isEmpty() {return this.file.length() == 0;}@Overridepublic long getSize() {return this.file.length();}@Overridepublic byte[] getBytes() throws IOException {return IOUtils.toByteArray(new FileInputStream(this.file));}@Overridepublic InputStream getInputStream() throws IOException {return new FileInputStream(this.file);}@Overridepublic void transferTo(File dest) throws IOException, IllegalStateException {// 可以直接使用File的transferTo方法this.file.renameTo(dest);}
}

在要转换处，编写方法：

public static MultipartFile convertInputStreamToFileMultipartFile(InputStream inputStream, String fileName, String contentType) throws IOException, IOException {Path tempFilePath = Files.createTempFile("temp-", fileName);Files.copy(inputStream, tempFilePath, StandardCopyOption.REPLACE_EXISTING);return new CustomMultipartFile(fileName, fileName, contentType, tempFilePath.toFile());}

核心转换逻辑伪代码

try {BufferedInputStream bis = null;URL url = new URL(photo_url);HttpURLConnection conn = (HttpURLConnection) url.openConnection();conn.setDoInput(true);conn.setRequestMethod("GET");conn.connect();InputStream inputStream = conn.getInputStream();logger.info(conn.getResponseMessage());bis = new BufferedInputStream(inputStream);MultipartFile multipartFile = convertInputStreamToFileMultipartFile(bis, "filename.txt", "text/plain");}catch(Exception e) {logger.error("文件下载/上传失败", e);} finally {// 清理临时文件（如果需要）}