SpringBoot學習筆記（12）：計劃任務

快速開始

　　本指南將指導您完成使用Spring安排任務的步驟。

參考教程：

https://spring.io/guides/gs/scheduling-tasks/

https://docs.spring.io/spring/docs/current/spring-framework-reference/integration.html#scheduling

使用Maven進行構建

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.springframework</groupId>
    <artifactId>gs-scheduling-tasks</artifactId>
    <version>0.1.0</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.3.RELEASE</version>
    </parent>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

創建一個計劃任務

import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;

import java.text.SimpleDateFormat;
import java.util.Date;

@Component
public class ScheduledTasks {
    private static final SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");

    @Scheduled(fixedRate = 1000)
    public void reportCurrentTime()
    {
        System.out.println(dateFormat.format(new Date()));
    }
}

　　@Schedule註釋定義特定方法何時運行。註意：此示例使用fixedRate，它指定從每次調用的開始時間開始測量的方法調用之間的間隔。還有其他選項，例如fixedDelay，它指定從完成任務開始測量的調用之間的間隔。您還可以使用@Scheduled（cron =“...”）表達式進行更復雜的任務調度。

如果您需要更為復雜的時間調度，請參考：

https://docs.spring.io/spring/docs/current/spring-framework-reference/integration.html#scheduling-annotation-support-scheduled

https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/scheduling/support/CronSequenceGenerator.html

http://www.manpagez.com/man/5/crontab/

"0 0 * * * *" = the top of every hour of every day.
"*/10 * * * * *" = every ten seconds.
"0 0 8-10 * * *" = 8, 9 and 10 o‘clock of every day.
"0 0 6,19 * * *" = 6:00 AM and 7:00 PM every day.
"0 0/30 8-10 * * *" = 8:00, 8:30, 9:00, 9:30, 10:00 and 10:30 every day.
"0 0 9-17 * * MON-FRI" = on the hour nine-to-five weekdays
"0 0 0 25 12 ?" = every Christmas Day at midnight

啟用計劃

@EnableScheduling確保創建後臺任務執行程序。沒有它，沒有任何安排。

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.scheduling.annotation.EnableScheduling;

@SpringBootApplication
@EnableScheduling
public class Application {

    public static void main(String[] args) throws Exception {
        SpringApplication.run(Application.class);
    }
}

測試

　　在控制臺按照規定間隔打印當前時間

SpringBoot學習筆記（12）：計劃任務