Scheduling Tasks

如果不知道如何使用 Spring，请先查看 Building a RESTful Web Service。

官方文章地址：https://spring.io/guides/gs/scheduling-tasks/

下载地址
git clone https://github.com/spring-guides/gs-scheduling-tasks.git

实现示例：使用 @Scheduled 每 5 秒输出当前时间。

build.gradle 文件：

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:1.5.2.RELEASE")
    }
}

apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'idea'
apply plugin: 'org.springframework.boot'

jar {
    baseName = 'gs-scheduling-tasks'
    version =  '0.1.0'
}

repositories {
    mavenCentral()
}

sourceCompatibility = 1.8
targetCompatibility = 1.8

dependencies {
    compile("org.springframework.boot:spring-boot-starter")
    testCompile("junit:junit")
}

src/main/java/hello/ScheduledTasks.java：

package hello;

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

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;

@Component
public class ScheduledTasks {

    private static final Logger log = LoggerFactory.getLogger(ScheduledTasks.class);

    private static final SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");

    @Scheduled(fixedRate = 5000)
    public void reportCurrentTime() {
        log.info("The time is now {}", dateFormat.format(new Date()));
    }
}

Scheduled 用于方法启动一个任务，fixedRate 指定任务的频率，这里是5000毫秒。其他选项查看 other options，使用 @Scheduled(cron=". . .") 指定更加复杂的任务，详情查看 这里。

src/main/java/hello/Application.java:

package hello;

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);
    }
}

@EnableScheduling 开启后台任务，否则不会启动 Scheduling。

输出信息如下：

2017-06-11 11:50:01.092  INFO 4351 --- [pool-1-thread-1] hello.ScheduledTasks                     : The time is now 11:50:01
2017-06-11 11:50:06.094  INFO 4351 --- [pool-1-thread-1] hello.ScheduledTasks                     : The time is now 11:50:06
2017-06-11 11:50:11.091  INFO 4351 --- [pool-1-thread-1] hello.ScheduledTasks                     : The time is now 11:50:11
2017-06-11 11:50:16.095  INFO 4351 --- [pool-1-thread-1] hello.ScheduledTasks                     : The time is now 11:50:16
2017-06-11 11:50:21.094  INFO 4351 --- [pool-1-thread-1] hello.ScheduledTasks                     : The time is now 11:50:21
2017-06-11 11:50:26.091  INFO 4351 --- [pool-1-thread-1] hello.ScheduledTasks                     : The time is now 11:50:26
2017-06-11 11:50:31.094  INFO 4351 --- [pool-1-thread-1] hello.ScheduledTasks                     : The time is now 11:50:31