file转为MultipartFile类型文件

以下是Java中File转为MultipartFile的四种方式：

1.使用MockMultipartFile类

File file = new("file.txt");
MockMultipartFile mockMultipartFile = new MockMultipartFile("file", new FileInputStream(file));

2.使用DiskFileItem类

File file = new File("file.txt");
DiskFileItem fileItem = new DiskFileItem("file", Files.probeContentType(file.toPath()), false, file.getName(), (int) file.length(), file.getParentFile());
fileItem.getOutputStream();
MultipartFile multipartFile = new CommonsMultipartFile(fileItem);

3.使用ByteArrayResource类

File file = new File("file.txt");
byte[] content = Files.readAllBytes(file.toPath());
ByteArrayResource resource = new ByteArrayResource(content);
MultipartFile multipartFile = new MockMultipartFile("file", file.getName(), Files.probeContentType(file.toPath()), resource.getInputStream());

4.使用InputStreamResource类

File file = new File("file.txt");
InputStreamResource resource = new InputStreamResource(new FileInputStream(file));
MultipartFile multipartFile = new MockMultipartFile("file", file.getName(), Files.probeContentType(file.toPath()), resource.getInputStream());