public interface IPollableService {
    /**
     * 執(zhí)行方法
     */
    void poll();

    /**
     * 獲取周期表達(dá)式
     *
     * @return CronExpression
     */
    default String getCronExpression() {
        return null;
    }

    /**
     * 獲取任務(wù)名稱
     *
     * @return 任務(wù)名稱
     */
    default String getTaskName() {
        return this.getClass().getSimpleName();
    }
}

@Configuration
@EnableAsync
@EnableScheduling
public class SchedulingConfiguration implements SchedulingConfigurer, ApplicationContextAware {
    private static final Logger log = LoggerFactory.getLogger(SchedulingConfiguration.class);
    private static ApplicationContext appCtx;
    private final ConcurrentMap<String, ScheduledTask> scheduledTaskHolder = new ConcurrentHashMap<>(16);
    private final ConcurrentMap<String, String> cronExpressionHolder = new ConcurrentHashMap<>(16);
    private ScheduledTaskRegistrar taskRegistrar;

    public static synchronized void setAppCtx(ApplicationContext appCtx) {
        SchedulingConfiguration.appCtx = appCtx;
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        setAppCtx(applicationContext);
    }

    @Override
    public void configureTasks(ScheduledTaskRegistrar taskRegistrar) {
        this.taskRegistrar = taskRegistrar;
    }

    /**
     * 刷新定時(shí)任務(wù)表達(dá)式
     */
    public void refresh() {
        Map<String, IPollableService> beanMap = appCtx.getBeansOfType(IPollableService.class);
        if (beanMap.isEmpty() || taskRegistrar == null) {
            return;
        }
        beanMap.forEach((beanName, task) -> {
            String expression = task.getCronExpression();
            String taskName = task.getTaskName();
            if (null == expression) {
                log.warn("定時(shí)任務(wù)[{}]的任務(wù)表達(dá)式未配置或配置錯誤，請檢查配置", taskName);
                return;
            }
            // 如果策略執(zhí)行時(shí)間發(fā)生了變化，則取消當(dāng)前策略的任務(wù)，并重新注冊任務(wù)
            boolean unmodified = scheduledTaskHolder.containsKey(beanName) && cronExpressionHolder.get(beanName).equals(expression);
            if (unmodified) {
                log.info("定時(shí)任務(wù)[{}]的任務(wù)表達(dá)式未發(fā)生變化，無需刷新", taskName);
                return;
            }
            Optional.ofNullable(scheduledTaskHolder.remove(beanName)).ifPresent(existTask -> {
                existTask.cancel();
                cronExpressionHolder.remove(beanName);
            });
            if (ScheduledTaskRegistrar.CRON_DISABLED.equals(expression)) {
                log.warn("定時(shí)任務(wù)[{}]的任務(wù)表達(dá)式配置為禁用，將被不會被調(diào)度執(zhí)行", taskName);
                return;
            }
            CronTask cronTask = new CronTask(task::poll, expression);
            ScheduledTask scheduledTask = taskRegistrar.scheduleCronTask(cronTask);
            if (scheduledTask != null) {
                log.info("定時(shí)任務(wù)[{}]已加載，當(dāng)前任務(wù)表達(dá)式為[{}]", taskName, expression);
                scheduledTaskHolder.put(beanName, scheduledTask);
                cronExpressionHolder.put(beanName, expression);
            }
        });
    }
}

@Component
public class CronTaskLoader implements ApplicationRunner {
    private static final Logger log = LoggerFactory.getLogger(CronTaskLoader.class);
    private final SchedulingConfiguration schedulingConfiguration;
    private final AtomicBoolean appStarted = new AtomicBoolean(false);
    private final AtomicBoolean initializing = new AtomicBoolean(false);

    public CronTaskLoader(SchedulingConfiguration schedulingConfiguration) {
        this.schedulingConfiguration = schedulingConfiguration;
    }

    /**
     * 定時(shí)任務(wù)配置刷新
     */
    @Scheduled(fixedDelay = 5000)
    public void cronTaskConfigRefresh() {
        if (appStarted.get() && initializing.compareAndSet(false, true)) {
            log.info("定時(shí)調(diào)度任務(wù)動態(tài)加載開始>>>>>>");
            try {
                schedulingConfiguration.refresh();
            } finally {
                initializing.set(false);
            }
            log.info("定時(shí)調(diào)度任務(wù)動態(tài)加載結(jié)束<<<<<<");
        }
    }

    @Override
    public void run(ApplicationArguments args) {
        if (appStarted.compareAndSet(false, true)) {
            cronTaskConfigRefresh();
        }
    }
}

@Service
public class CronTaskBar implements IPollableService {
    @Override
    public void poll() {
        System.out.println("Say Bar");
    }

    @Override
    public String getCronExpression() {
        return "0/1 * * * * ?";
    }
}

@Service
public class CronTaskFoo implements IPollableService {
    private static final Random random = new SecureRandom();

    @Override
    public void poll() {
        System.out.println("Say Foo");
    }

    @Override
    public String getCronExpression() {
        return "0/" + (random.nextInt(9) + 1) + " * * * * ?";
    }
}

@Service
public class CronTaskUnavailable implements IPollableService {
    private String cronExpression = "-";
    private static final Map<String, String> map = new HashMap<>();

    static {
        map.put("-", "0/1 * * * * ?");
        map.put("0/1 * * * * ?", "-");
    }

    @Override
    public void poll() {
        System.out.println("Say Unavailable");
    }

    @Override
    public String getCronExpression() {
        return (cronExpression = map.get(cronExpression));
    }
}