未找到轴突3处理程序

我是Java初学者。我将只为工作和处理命令配置我的处理程序。此时此刻,我收到 Exception No handler was subscribed to command [com.capgemini.books.CreateBook] .

我的代码看起来像:

@Configuration
public class ControllerConfig {
    @Bean
    public CommandBus commandBus() {
        return new SimpleCommandBus();
    }
}

public class CreateBookHandler {
    public CreateBookHandler() { }

    @CommandHandler
    public void handle(CreateBook command) {
       Book newBook = new Book(1001L, "anonymous", command.bookTitle());
    }
}