（给
ImportNew加星标，提高Java技能）
一、引言
为了满足不同环境和需求的变化，我们需要让自己写的代码涉及面更加广泛，为了支持不同平台的对象，我决定设计一个支持各种平台的文件上传，删除功能，相信一点能满足你的需求。二、介绍主角
- @ConditionalOnProperty：根据指定的属性值条件，决定是否创建该组件的实例。这使得组件的创建可以根据配置文件中的属性进行动态控制。
- @ConfigurationProperties：将配置文件中的属性值绑定到该类的字段上，实现属性的自动注入。这样可以方便地从配置文件中读取和使用属性值。
下面是一个简单的案例
首先，定义一个文件上传接口 FileUploadService，其中包含文件上传的方法：public interface FileUploadService { void uploadFile(MultipartFile file);}
然后，创建不同平台的文件上传实现类，例如 LocalFileUploadService 和 S3FileUploadService：@Component@ConditionalOnProperty(value = "file.upload.platform", havingValue = "local")public class LocalFileUploadService implements FileUploadService { @Override public void uploadFile(MultipartFile file) { System.out.println("Uploading file to local platform..."); }}
@Component@ConditionalOnProperty(value = "file.upload.platform", havingValue = "s3")public class S3FileUploadService implements FileUploadService { @Override public void uploadFile(MultipartFile file) { System.out.println("Uploading file to S3 platform..."); }}
通过在配置文件（例如 application.properties）中设置 file.upload.platform 属性的值，可以选择性地使用不同平台的文件上传实现类：file.upload.platform=local
这样，你就可以根据需要选择性地实现不同平台的文件上传接口，并通过配置文件来控制使用哪个实现类。三、具体编写
3.1 构思
我们需要对上传文件进行自定义校验，比如文件名，文件大小、文件后缀判断、对文件重命名等等，这些都是每个接口可能需要实现的内容，我们不可能让每个接口都去实现，这样就会造成以下情况:
public class LocalFileStorage{ public String uploadFile(String dir, MultipartFile file, String[] allowedExtension) { }
}
public class AliyunFileStorage{
public String uploadFile(String dir, MultipartFile file, String[] allowedExtension) { } }
public class TencentFileStorage{
public String uploadFile(String dir, MultipartFile file, String[] allowedExtension) { } }
这让我想到了，AOP（Aspect Oriented Programming）,我们可以对接口进行切面，在切面中实现这些不就好了？这样一下就解决了第 1 点和第 2 点。第 3 点：构思的解决方案主要是在接口上进行扩展，很好解决。第 4 点：在文章开始已经说明，采用 @ConditionalOnProperty(..) 即可.3.2 “赛前” 准备工作
媒体类型定义
public class MimeTypeConstant {
public static final String[] IMAGE_EXTENSION = {"bmp", "gif", "jpg", "jpeg", "png"};
public static final String[] FLASH_EXTENSION = {"swf", "flv"};
public static final String[] MEDIA_EXTENSION = {"swf", "flv", "mp3", "wav", "wma", "wmv", "mid", "avi", "mpg", "asf", "rm", "rmvb"};
public static final String[] VIDEO_EXTENSION = {"mp4", "avi", "rmvb"};
public static final String[] DEFAULT_ALLOWED_EXTENSION = { "bmp", "gif", "jpg", "jpeg", "png", "doc", "docx", "xls", "xlsx", "ppt", "pptx", "html", "htm", "txt", "rar", "zip", "gz", "bz2", "mp4", "avi", "rmvb", "pdf"};}
配置类定义
用于读取配置类中一些基础配置方便后续根据用户配置进行校验。@Component@ConfigurationProperties(prefix = "file.storage")@Datapublic class FileStorageConfig { private String type = "local"; private String[] allowedExtension = IMAGE_EXTENSION; private int fileNameLength = 100; private boolean coverFileName = true;
}
FileUtils 工具类编写
public class FileUtils {
public static final String DOT = ".";
public static final DateTimeFormatter FORMATTER = DateTimeFormatter.ofPattern("yyyy" + File.separator + "MM" + File.separator + "dd" + File.separator);
public static boolean isAllowedExtension(String extension, String[] allowedExtension) { for (String str : allowedExtension) { if (str.equalsIgnoreCase(extension)) { return true; } } return false; }
public static String getFileExtension(MultipartFile file) { String originalFilename = file.getOriginalFilename(); if (originalFilename == null) { throw new RuntimeException("FileUtils: originalFilename is null"); } String fileExtension; int lastDotIndex = originalFilename.lastIndexOf('.'); if (lastDotIndex > 0) { fileExtension = originalFilename.substring(lastDotIndex + 1); } else { MimeType mimeType = MimeTypeUtils.parseMimeType(Objects.requireNonNull(file.getContentType())); fileExtension = mimeType.getSubtype(); } return fileExtension; }
public static String correctAndJoinPaths(String... paths) { StringBuilder result = new StringBuilder(); for (String path : paths) { if (path != null && !path.isEmpty()) { if (!result.isEmpty() && result.charAt(result.length() - 1) != File.separatorChar && !path.startsWith(File.separator)) { result.append(File.separator); } result.append(path.replaceAll("[" + File.separator + "/\\]+$", "")); } } if (!result.isEmpty() && result.charAt(result.length() - 1) != File.separatorChar) { result.append(File.separator); } return result.toString(); }
public static String datePath() { return LocalDate.now().format(FORMATTER); }
}
3.3 编写代码
定义 FileStorageService 接口
- 这个接口提供了一组方法来处理文件上传和删除的操作，并提供了一些默认实现来简化使用。你可以根据自己的需求实现该接口，并在实现类中提供具体的上传和删除逻辑。
- 虽然看着接口内容很多，但是实现者只需要实现 uploadFile() , deleteFile() 即可。
public interface FileStorageService { String uploadFile(String dir, MultipartFile file, String[] allowedExtension);
default String[] uploadFiles(String dir, MultipartFile[] files, String[] allowedExtension) { return Arrays.stream(files).map(file -> this.uploadFile(dir, file, allowedExtension)).toArray(String[]::new); }
boolean deleteFile(String dir, String url);
default boolean deleteFiles(String dir, String[] urls) { return Arrays.stream(urls).allMatch(url -> this.deleteFile(dir, url)); }
default boolean deleteFile(String url) { return deleteFile("", url); }
default boolean deleteFiles(String[] urls) { return Arrays.stream(urls).allMatch(this::deleteFile); }
default String uploadFile(String dir, MultipartFile file) {
return uploadFile(dir, file, null); }
default String uploadFile(MultipartFile file, String[] allowedExtension) { return uploadFile("", file, allowedExtension); }
default String uploadFile(MultipartFile file) { return uploadFiles("", new MultipartFile[]{file}, null)[0]; }
default String[] uploadFiles(String dir, MultipartFile[] files) { return Arrays.stream(files).map(file -> this.uploadFile(dir, file)).toArray(String[]::new); }
default String[] uploadFiles(MultipartFile[] files, String[] allowedExtension) { return Arrays.stream(files).map(file -> this.uploadFile(file, allowedExtension)).toArray(String[]::new); }
default String[] uploadFiles(MultipartFile[] files) { return Arrays.stream(files).map(this::uploadFile).toArray(String[]::new); }
}
本地上传进行实现
接口对应实现，这里只给出本地文件上传的实现方法，其他方法类似。@Component@ConditionalOnProperty(value = "file.storage.type", havingValue = "local", matchIfMissing = true)@ConfigurationProperties(prefix = "file.storage.local")@RequiredArgsConstructor@Datapublic class LocalFileStorageImpl implements FileStorageService {
private static final Logger log = LoggerFactory.getLogger(LocalFileStorageImpl.class); private String uploadPath; private String accessUrl = "/images";
@Bean public WebMvcConfigurer resourceHandlerConfigurer() { return new WebMvcConfigurer() { @Override public void addResourceHandlers(ResourceHandlerRegistry registry) { String fileUploadPath = FileUtils.correctAndJoinPaths(uploadPath); registry.addResourceHandler(accessUrl + "/**").addResourceLocations("file:" + fileUploadPath); } }; }
@Override public String uploadFile(String dir, MultipartFile file, String[] allowedExtension) { String absolutePath = FileUtils.correctAndJoinPaths(uploadPath, dir, FileUtils.datePath()); try { File absoluteFile = getAbsoluteFile(absolutePath, file.getOriginalFilename()); file.transferTo(absoluteFile); } catch (IOException e) { log.error("上传文件失败, 常见错误: 未开启路径权限: {}", absolutePath); throw new ServiceException(ResultCode.FILE_UPLOAD_ERROR); } return getRequestFileName(file, accessUrl + "/" + dir + "/" + FileUtils.datePath()); }
@Override public boolean deleteFile(String dir, String url) { String fileName = extractFileNameFromUrl(url); String absolutePath = FileUtils.correctAndJoinPaths(uploadPath, dir, fileName); File file = new File(absolutePath); if (file.exists()) { if (!file.delete()) { log.error("File deletion failed: {}", absolutePath); return false; } } else { log.warn("File does not exist for deletion: {}", absolutePath); return false; } return true; }
private String getRequestFileName(MultipartFile file, String accessUrl) { HttpServletRequest request = ((ServletRequestAttributes) Objects.requireNonNull(RequestContextHolder.getRequestAttributes())).getRequest(); String baseUrl = request.getRequestURL().toString().replace(request.getRequestURI(), request.getContextPath()); String originalFilename = file.getOriginalFilename(); String requestFileName = baseUrl + accessUrl + originalFilename; return requestFileName.replace("//", "/").replace(File.separator, "/"); }
private File getAbsoluteFile(String uploadDir, String fileName) { File desc = new File(uploadDir + fileName); if (!desc.exists()) { if (!desc.getParentFile().exists()) { desc.getParentFile().mkdirs(); } } return desc; }
