springboot3生成本地文件url的实现示例

custom:
  upload:
    avatar_dir: ${user.dir}/avatar_dir/
    avatar_dir_name: avatar_dir

@Data
@Configuration
@ConfigurationProperties(prefix = "custom.upload")
public class FileUploadConfig {
   private String avatarDir;
   private String avatarDirName;
}

@Configuration
public class WebConfig implements WebMvcConfigurer {
    @Autowired
    FileUploadConfig uploadConfig;

    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        File file = new File(uploadConfig.getAvatarDir());
        String path = "file:" + file + File.separator;
        // 匹配 http://ip:port/avatar_dir/ 下的所有文件
        registry.addResourceHandler("/avatar_dir/**")
                // 实际静态文件地址
                .addResourceLocations(path);
    }
}

@Service
public interface FileService {
	// 获取图像 Url
    public Result<String> getImageUrl(User user, String host, int port);
	// 路径拼接
    public String joinPaths(String... paths);
}

String imageUrl = String.format(
	"http://%s:%d/%s", host, port, joinPaths(
  								  		uploadConfig.getAvatarDirName(), 
  								  		avatar
  							  		)
);

@Service
public class FileServiceImpl implements FileService {
    @Autowired
    FileUploadConfig uploadConfig;

    @Autowired
    IUserService userService;

	// 路径拼接
    @Override
    public String joinPaths(String... paths) {
        Path resultPath = Paths.get("");
        for (String path : paths) {
            resultPath = resultPath.resolve(path);
        }
        return resultPath.toString();
    }
    
    // 判断文件是否存在
    private Boolean isUserAvatarExists(String avatar) {
        String path = joinPaths(uploadConfig.getAvatarDir(), avatar);
        File filePath = new File(path);
        return filePath.exists();
    }

	// 获取图像 Url
    @Override
    public Result<String> getImageUrl(User user, String host, int port) {
    	// 用户头像的文件名唯一，并保存在了数据库中，avatar = xxx.png
        String avatar = this.userService.getById(user.getUserId()).getAvatar();
        
        if (isUserAvatarExists(avatar)) {
            String imageUrl = String.format("http://%s:%d/%s", host, port, joinPaths(uploadConfig.getAvatarDirName(), avatar));
            return Result.successfulResult("获取成功", imageUrl);
        }
        return Result.errorResult("文件丢失");
    }
}

@Tag(name = "文件上传接口")
@RestController
@RequestMapping("/sign/file")
public class FileUploadController {
    @Autowired
    FileService fileService;

    @Operation(summary = "获取图片 URL")
    @PostMapping("/image/get")
    public Result<String> getImageUrl(@RequestBody User user) {
        URI currentUri = ServletUriComponentsBuilder.fromCurrentRequestUri().build().toUri();
        // currentUri.getHost() 获取请求 IP，如 localhost
        // currentUri.getPort() 获取请求 端口号，如 8080
        return fileService.getImageUrl(user, currentUri.getHost(), currentUri.getPort());
    }
}