对动态修改定时任务的补充

对动态修改定时任务的补充

上篇文章讲到通过定时任务动态修改定时任务的执行时间，看到有很多人喜欢，特地在此感谢，同时在这里对方案二再进行优化，增加了对时区的支持，同时去掉了自定义注解DynamicCron，默认支持所有@Scheduled的定时任务。

优化如下：

package com.lakala.zf.svas.scheduling;

import lombok.extern.slf4j.Slf4j;
import org.jetbrains.annotations.NotNull;
import org.springframework.context.EmbeddedValueResolverAware;
import org.springframework.lang.Nullable;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.scheduling.annotation.SchedulingConfigurer;
import org.springframework.scheduling.config.CronTask;
import org.springframework.scheduling.config.ScheduledTaskRegistrar;
import org.springframework.scheduling.support.CronTrigger;
import org.springframework.stereotype.Component;
import org.springframework.util.StringUtils;
import org.springframework.util.StringValueResolver;

import java.lang.reflect.Method;
import java.util.*;

@Slf4j
@Component
public class SchedulingConfig implements SchedulingConfigurer, EmbeddedValueResolverAware {

    @Nullable
    private StringValueResolver embeddedValueResolver;

    @Override
    public void configureTasks(ScheduledTaskRegistrar taskRegistrar) {
        List<CronTask> cronTaskList = new ArrayList<>(taskRegistrar.getCronTaskList());
        Iterator<CronTask> iterator = cronTaskList.iterator();
        while (iterator.hasNext()) {
            CronTask cronTask = iterator.next();
            String fullPath = cronTask.toString();
            log.info("cronTaskList:{}", fullPath);
            Scheduled scheduled = getDynamicCron(fullPath);
            // Check cron expression
            String zone = scheduled.zone();
            if (this.embeddedValueResolver != null) {
                zone = this.embeddedValueResolver.resolveStringValue(zone);
            }
            TimeZone timeZone;
            if (StringUtils.hasText(zone)) {
                timeZone = StringUtils.parseTimeZoneString(zone);
            } else {
                timeZone = TimeZone.getDefault();
            }
            iterator.remove();
            taskRegistrar.addTriggerTask(cronTask.getRunnable(), triggerContext -> {
                CronTrigger trigger =
                        new CronTrigger(Objects.requireNonNull(this.embeddedValueResolver.resolveStringValue(scheduled.cron())), timeZone);
                return trigger.nextExecutionTime(triggerContext);
            });
            log.info("addTriggerTask:{}", cronTask);
        }
        taskRegistrar.setCronTasksList(cronTaskList);
    }


    private Scheduled getDynamicCron(String fullPath) {
        try {
            int lastDotIndex = fullPath.lastIndexOf('.');
            // 加载类
            Class<?> clazz = Class.forName(fullPath.substring(0, lastDotIndex));
            // 获取方法
            Method method = clazz.getDeclaredMethod(fullPath.substring(lastDotIndex + 1));
            // 获取注解
            return method.getAnnotation(Scheduled.class);
        } catch (Exception e) {
            log.error("getAnnotation err", e);
            throw new RuntimeException(e);
        }
    }

    @Override
    public void setEmbeddedValueResolver(@NotNull StringValueResolver resolver) {
        this.embeddedValueResolver = resolver;
    }

}

实现逻辑

具体看ScheduledAnnotationBeanPostProcessor，这个类是 Spring 对定时任务处理的逻辑，这也充分说明了为什么定时任务是放在 cronTasks，而不是 triggerTasks，具体逻辑请看org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor#processScheduled方法，源码很清晰，在此就不解读了，如果有朋友感兴趣，可以在评论区评论，点赞多的话我会详细解读一下，还是蛮有意思的。