一文彻底弄懂Java中MultipartFile接口和File类

public interface MultipartFile extends InputStreamSource {
    String getName();

    @Nullable
    String getOriginalFilename();

    @Nullable
    String getContentType();

    boolean isEmpty();

    long getSize();

    byte[] getBytes() throws IOException;

    InputStream getInputStream() throws IOException;

    default Resource getResource() {
        return new MultipartFileResource(this);
    }

    void transferTo(File dest) throws IOException, IllegalStateException;

    default void transferTo(Path dest) throws IOException, IllegalStateException {
        FileCopyUtils.copy(this.getInputStream(), Files.newOutputStream(dest));
    }
}

public void transferTo(File dest) throws IOException, IllegalStateException {
        if (!this.isAvailable()) {
            throw new IllegalStateException("File has already been moved - cannot be transferred again");
        } else if (dest.exists() && !dest.delete()) {
            throw new IOException("Destination file [" + dest.getAbsolutePath() + "] already exists and could not be deleted");
        } else {
            try {
                this.fileItem.write(dest);
                LogFormatUtils.traceDebug(logger, (traceOn) -> {
                    String action = "transferred";
                    if (!this.fileItem.isInMemory()) {
                        action = this.isAvailable() ? "copied" : "moved";
                    }

                    return "Part '" + this.getName() + "',  filename '" + this.getOriginalFilename() + "'" + (traceOn ? ", stored " + this.getStorageDescription() : "") + ": " + action + " to [" + dest.getAbsolutePath() + "]";
                });
            } catch (FileUploadException var3) {
                throw new IllegalStateException(var3.getMessage(), var3);
            } catch (IOException | IllegalStateException var4) {
                throw var4;
            } catch (Exception var5) {
                throw new IOException("File transfer failed", var5);
            }
        }
    }

// 获取上传文件的原始文件名
String originalFilename = StringUtils.cleanPath(file.getOriginalFilename());

// 构建目标文件对象
File destFile = new File("/path/to/destination/directory", originalFilename);

try {
    // 将上传文件保存到目标文件
    file.transferTo(destFile);
    return "File uploaded successfully!";
} catch (IOException e) {
    e.printStackTrace();
    return "Failed to upload the file.";
}

// 构建目标文件路径
String uploadDirectory = "/path/to/destination/directory";
String originalFilename = file.getOriginalFilename();
Path filePath = Paths.get(uploadDirectory, originalFilename);

try {
// 将上传文件保存到目标文件
    file.transferTo(filePath);
    return "File uploaded successfully!";
} catch (IOException e) {
    e.printStackTrace();
    return "Failed to upload the file.";
}