我嘗試實現一個 REST 服務，如本教程中所示： 教程但我收到了這個錯誤：Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'fileStorageService' defined in file: Bean instantiation via constructor failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.airgnb.service.FileStorageService]: Constructor threw exception; nested exception is java.lang.NullPointerExceptionCaused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.airgnb.service.FileStorageService]: Constructor threw exception; nested exception is java.lang.NullPointerExceptionCaused by: java.lang.NullPointerException服務等級：@Servicepublic class FileStorageService {    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 FileStorageServiceException("Could not create the directory where the uploaded files will be stored.", ex);        }    }}配置類別：@Configuration@ConfigurationProperties(prefix = "file")public class FileStorageProperties {    private String uploadDir;    public String getUploadDir() {        return uploadDir;    }    public void setUploadDir(String uploadDir) {        this.uploadDir = uploadDir;    }}該應用程序也注釋如下：@SpringBootApplication@EnableConfigurationProperties({FileStorageProperties.class})public class TestApp implements InitializingBean {我認為唯一不同的是我使用 application.yml 而不是 application.properties，但我定義的屬性與教程類似，但只是采用 yml 樣式。我不知道為什么FileStorageProperties沒有注入，因此FileStorageService無法創建。@Import(FileStoroageProperties.class)我已經嘗試使用其他一些依賴注入方式（例如字段注入）來注釋應用程序。