java Spring 计划任务不会在应用程序启动时启动
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Spring Scheduled task does not start on application startup
提问by v1shnu
I have a @Scheduledtask in my application which is setup using CRONand run every 4 hours. The problem I face is that the CRONjob does not start immediately after application startup but it starts only 4 hours after the application startup.
@Scheduled我的应用程序中有一项任务，该任务设置使用CRON并每 4 小时运行一次。我面临的问题是该CRON作业不会在应用程序启动后立即启动，而是在应用程序启动后仅 4 小时启动。
I tried to use a @PostConstructmethod inside the task to invoke it, but that results in an error due to an uninitialized Spring context.
我尝试@PostConstruct在任务中使用一个方法来调用它，但由于未初始化的 Spring 上下文导致错误。
Please tell me how I can make the Scheduled task run immediately on application deployment and then on every 4 hours after the deployment.
请告诉我如何在应用程序部署时立即运行计划任务，然后在部署后每 4 小时运行一次。
EDIT:
I would not use a @PostConstructsince my scheduled method depends on other Beans , which are not initialized when this PostConstruct method runs for some reason.
编辑：
我不会使用 a@PostConstruct因为我的计划方法依赖于其他 Beans ，当这个 PostConstruct 方法由于某种原因运行时没有初始化。
回答by Tomas F.
By 0 */4 * * * you specify "At minute 0 past every 4th hour (0:00, 4:00, 8:00 etc.)", which is not at startup time and then every 4 hours as I think you want. You can specify initial delay and rate by:
通过 0 */4 * * * 您指定“每 4 小时后的第 0 分钟（0:00、4:00、8:00 等）”，这不是在启动时间，然后是我认为的每 4 小时想。您可以通过以下方式指定初始延迟和速率：
@Scheduled(initialDelay=0, fixedRate=4*60*60*1000)
If you are worried about hard-coded values, you can still provide config value:
如果您担心硬编码值，您仍然可以提供配置值：
@Scheduled(initialDelay=0, fixedRateString = "${some.config.string}")
回答by Murugapandian Ramaiah
I had @EnableSchedulingin my app config. I had
@Scheduled(fixedDelay=5000)in my scheduled task class. Even then it didn't work.
我@EnableScheduling在我的应用程序配置中有。我
@Scheduled(fixedDelay=5000)在我的计划任务课上。即使那样也没有奏效。
I added @Serviceto my scheduled task class and everything worked fine.
我添加@Service到我的计划任务类，一切正常。
回答by Dherik
If is not possible to use initialDelayattribute with the cronrule and your intention is execute this Job after every restart, you can implement a CommandLineRunneron your application class:
如果无法将initialDelay属性与cron规则一起使用，并且您的意图是在每次重新启动后执行此作业，您可以CommandLineRunner在您的应用程序类上实现：
@SpringBootApplication
public class MyApplication implements CommandLineRunner {
public static void main(String[] args) {
SpringApplication.run(MyApplication.class, args);
}
@Autowired
private TaskService taskService;
@Override
public void run(final String... args) throws Exception {
taskService.run();
}
}
It's not the best strategy, but works.
这不是最好的策略，但有效。
回答by px06
I'm not sure if you have tried this but you can use @Scheduledwith an initialDelay
我不知道，如果你已经尝试过这一点，但你可以用@Scheduled用initialDelay
For fixed-delay and fixed-rate tasks, an initial delay may be specified indicating the number of milliseconds to wait before the firstexecution of the method.
对于固定延迟和固定速率任务，可以指定初始延迟，指示在第一次执行该方法之前等待的毫秒数。
@Scheduled(initialDelay=0, fixedRate=5000)
public void doSomething() {
// something that should execute periodically
}
I assume this will execute your scheduled method when the application is run.
我假设这将在应用程序运行时执行您的计划方法。
回答by Monzurul Haque Shimul
Instead of cron inside @Scheduled, use fixedRate like below. By default initialDelay is -1, which will start immediately or you can set 0.
而不是 @Scheduled 中的 cron，使用如下所示的 fixedRate。默认initialDelay 是-1，它会立即开始或者你可以设置为0。
@Scheduled(fixedRate=4*60*60*1000)
public void test() {
System.out.println("helloworld");
}
回答by Andrei Balici
Just specify the method you want to run in the init_methodattribute of the bean.
只需init_method在 bean的属性中指定要运行的方法即可。
Java config: @Bean(init_method="methodWhichStartsTask")
Java配置： @Bean(init_method="methodWhichStartsTask")
XML config: <bean id="someId" class="com.example.Clazz" init-method="methodWhichStartsTask"/>
XML 配置： <bean id="someId" class="com.example.Clazz" init-method="methodWhichStartsTask"/>
This will invoke the method just after the bean is properly initialized and if the method is scheduled, then it will be called afterwards every 4 hours.
这将在 bean 正确初始化后立即调用该方法，如果该方法已调度，则此后每 4 小时将调用一次。
回答by Vishal Patel
I was having the same situation. I need to run cron scheduler every 1st day of the month and also when the application starts.
我遇到了同样的情况。我需要在每个月的第一天以及应用程序启动时运行 cron 调度程序。
This is how I achieved using ApplicationListener.
这就是我使用 ApplicationListener 实现的方式。
import org.springframework.context.ApplicationListener;
import org.springframework.boot.context.event.ApplicationReadyEvent;
@Component
public class ApplicationReadyListner implements ApplicationListener<ApplicationReadyEvent> {
@Override
public void onApplicationEvent(ApplicationReadyEvent event) {
// callYourTask();
}
}
回答by M2E67
user @EnableScheduling annotation on your class which contains you1 scheduled method:
您的类上的用户 @EnableScheduling 注释，其中包含您 1 个预定的方法：
see spring document:
参见弹簧文档：
To enable support for @Scheduled and @Async annotations add @EnableScheduling and @EnableAsync to one of your @Configuration classes:
要启用对 @Scheduled 和 @Async 注释的支持，请将 @EnableScheduling 和 @EnableAsync 添加到您的 @Configuration 类之一：
@Configuration
@EnableAsync
@EnableScheduling
public class AppConfig {
}
link : https://docs.spring.io/spring/docs/current/spring-framework-reference/html/scheduling.html
链接：https: //docs.spring.io/spring/docs/current/spring-framework-reference/html/scheduling.html
