注入点有以下注释： - @org.springframework.beans.factory.annotation.Autowired(required=true)

Question

我是 Spring Boot 的新手，在编写文件上传 API 时出现以下错误：

Error:Description:
Field fileStorageService in com.primesolutions.fileupload.controller.FileController required a bean of type 'com.primesolutions.fileupload.service.FileStorageService' that could not be found.
The injection point has the following annotations:
    - @org.springframework.beans.factory.annotation.Autowired(required=true)
Action:
Consider defining a bean of type 'com.primesolutions.fileupload.service.FileStorageService' in your configuration.*

控制器类：

public class FileController 
{
    private static final Logger logger = LoggerFactory.getLogger(FileController.class);

    @Autowired
    private FileStorageService fileStorageService;

    @PostMapping("/uploadFile")
    public UploadFileResponse uploadFile(@RequestParam("file") MultipartFile file) {
        String fileName = fileStorageService.storeFile(file);

        String fileDownloadUri = ServletUriComponentsBuilder.fromCurrentContextPath()
                .path("/downloadFile/")
                .path(fileName)
                .toUriString();

        return new UploadFileResponse(fileName, fileDownloadUri,
                file.getContentType(), file.getSize());
    }

    @PostMapping("/uploadMultipleFiles")
    public List<UploadFileResponse> uploadMultipleFiles(@RequestParam("files") MultipartFile[] files) {
        return Arrays.asList(files)
                .stream()
                .map(file -> uploadFile(file))
                .collect(Collectors.toList());
    }
}

服务等级：

private final Path fileStorageLocation;


    @Autowired
    public FileStorageService(FileStorageProperties fileStorageProperties) {
        this.fileStorageLocation = Paths.get(fileStorageProperties.getUploadDir())
                .toAbsolutePath().normalize();

        try {
            Files.createDirectories(this.fileStorageLocation);
        } catch (Exception ex) {
            throw new FileStorageException("Could not create the directory where the uploaded files will be stored.", ex);
        }
    }

    public String storeFile(MultipartFile file) {
        // Normalize file name
        String fileName = StringUtils.cleanPath(file.getOriginalFilename());

        try {
            // Check if the file's name contains invalid characters
            if(fileName.contains("..")) {
                throw new FileStorageException("Sorry! Filename contains invalid path sequence " + fileName);
            }

            // Copy file to the target location (Replacing existing file with the same name)
            Path targetLocation = this.fileStorageLocation.resolve(fileName);
            Files.copy(file.getInputStream(), targetLocation, StandardCopyOption.REPLACE_EXISTING);

            return fileName;
        } catch (IOException ex) {
            throw new FileStorageException("Could not store file " + fileName + ". Please try again!", ex);
        }
    }

配置类：

@ConfigurationProperties(prefix = "file")
public class FileStorageProperties {

    private String uploadDir;

    public String getUploadDir()
    {
        return uploadDir;
    }

    public void setUploadDir(String uploadDir) {
        this.uploadDir = uploadDir;
    }
}

主要的：

@SpringBootApplication
@EnableConfigurationProperties({
        FileStorageProperties.class
})
public class FileApplication {
    public static void main(String[] args) {
        SpringApplication.run(FileApplication.class, args);
    }
}

属性文件

## MULTIPART (MultipartProperties)
# Enable multipart uploads
spring.servlet.multipart.enabled=true
# Threshold after which files are written to disk.
spring.servlet.multipart.file-size-threshold=2KB
# Max file size.
spring.servlet.multipart.max-file-size=200MB
# Max Request Size
spring.servlet.multipart.max-request-size=215MB

## File Storage Properties
# All files uploaded through the REST API will be stored in this directory
file.upload-dir=C:/Projects/SpringBootProject/Primesolutions/PrimeSolutions/FileUpload

我正在尝试读取文件上传属性并将其传递给控制器​​类。

Answer 1

我使用 @Autowired 注释解决了这个问题，只需替换为这个`

@Autowired(required = false)

`

Answer 2

该错误似乎表明 Spring 不知道任何类型的 bean com.primesolutions.fileupload.service.FileStorageService。

正如评论中所说，请确保您的课程FileStorageService由@Serviceor注释@Component：

@Service
public class FileStorageService {
...
}

还要确保此类位于您的 class 的子包中FileApplication。例如，如果您的FileApplication类位于包中com.my.package，请确保您FileStorageService的类位于包 com.my.package.** （相同包或任何子包）中。

顺便说一下，改进代码的一些注意事项：

• 当您的类只有一个非默认构造函数时，构造函数上的使用@Autowired是可选的。

• 不要在构造函数中放入太多代码。改用@PostConstruct注释。

    @Service
    public class FileStorageService {
        private FileStorageProperties props;
        // @Autowired is optional in this case
        public FileStorageService (FileStorageProperties fileStorageProperties) {
            this.props = fileStorageProperties;
            this.fileStorageLocation = Paths.get(fileStorageProperties.getUploadDir())
                    .toAbsolutePath().normalize();
        }

        @PostConstruct
        public void init() {
            try {
                Files.createDirectories(this.fileStorageLocation);
            } catch (Exception ex) {
                throw new FileStorageException("Could not create the directory where the uploaded files will be stored.", ex);
            }
        }
    }

• 最好避免@Autowired在场上。改用构造函数。它更适合您的测试，并且更易于维护：

public class FileController {
    private FileStorageService service;

    public FileController(FileStorageService service) {
        this.service = service;
    }
}