Spring Unable to fetch value from DB for a cron expression and use it in @Scheduled annotation to run my Scheduler

Am Unable to fetch value from DB for a cron expression and use it in @Scheduled annotation to run my Scheduler

my project is spring boot reactive with Postgres db

am using jdk17 spring-boot-starter-parent 3.1.4 Postgres version "PostgreSQL 16.0 on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 7.5.0-3ubuntu1~18.04) 7.5.0, 64-bit"

@Component
public class MyScheduler {
  private final myCronExpressionFetcherFetcherServiceImpl myCronExpressionFetcherService;


@Scheduled(cron = "#{@myCronExpressionFetcherService.getCronExpression()}")
  public void checkAndProcessInProgressAppointments() {
    TaskSchedulerConfig taskSchedulerConfig = myCronExpressionFetcherRepo.findByTaskName("PENDING_TASKS_SCHEDULER").block();

    // my task

  }


}


@Repository
public interface MyCronExpressionFetcherRepo extends ReactiveCrudRepository<TaskSchedulerConfig, Long> {
    Mono<TaskSchedulerConfig> findByTaskName(String taskName);



}


@Table(name = TABLE_MY_SCHDULER_CONFIG)
@Data
@Builder
public class TaskSchedulerConfig {
    @Id
    private Long id;
    private String taskName;
    private String cronExpression;
    private boolean enabled;
}


@Service
public class MyCronExpressionFetcherFetcherServiceImpl  {

  private final MyCronExpressionFetcherRepo tasCronExpressionFetcherRepo;

  public Mono<String> getCronExpression() {
    log.info("Fetching cron expression for task: {}", PENDING_TASKS_SCHEDULER);

    return tasCronExpressionFetcherRepo.findByTaskName(PENDING_TASKS_SCHEDULER)
        .map(taskSchedulerConfig -> {
          if (taskSchedulerConfig != null) {
            log.info("Fetched cron expression: {}", taskSchedulerConfig.getCronExpression());
            return taskSchedulerConfig.getCronExpression();
          } else {
            log.info("TaskSchedulerConfig not found. Using default cron expression.");
            return "";
          }
        });
  }

i felt like SpeL with reactive in combination of @Scheduled is not working. i am getting error like Unable to evaluate expression and a Bean is not found for my Impl class but my Impl class is with @Service annotation.

Comment From: snicoll

i felt like SpeL with reactive in combination of @scheduled is not working.

Invoking a reactive method with SpEL is not supported indeed. You are conflating two different models here. The cron expression is retrieved on startup, the reactive pipeline is not ready yet. A database call also means that you're making the whole data layer dependent on that particular bean.

i am getting error like Unable to evaluate expression and a Bean is not found for my Impl class but my Impl class is with @service annotation.

Going forward, please take some time to make the report more actionable. Rather than pasting code in text and not providing the actual exception,share a small sample we can run ourselves in the form of a zip attached to the issue or a link to a GitHub repository.