前言

@Scheduled適用與監聽任務較少的，而Quartz適合較多的，為確保可伸縮性，Quartz採用了基於多執行緒的架構。啟動時，框架初始化一套worker執行緒，這套執行緒被排程器用來執行預定的作業。這就是Quartz怎樣能併發執行多個作業的原理。Quartz依賴一套鬆耦合的執行緒池管理部件來管理執行緒環境。 

實現定時器的方式有兩種：

• Scheduled：spring 3.0 後自帶的定時器
• Quartz：第三放定時器框架

1.Scheduled

1.1建立任務類

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

import java.util.Date;

@Component
public class Schedule {

    @Scheduled(fixedRate = 2000)
    public void task() {
        System.out.println("啟動定時任務:" + new Date());
    }
}
 

使用 @Scheduled 定義任務執行時間，程式碼中表示每隔 2 秒執行一次任務。

1.2啟動定時任務

在啟動類上新增@EnableScheduling

測試結果：

2.Quartz

2.1匯入依賴

        <dependency>
            <groupId>org.quartz-scheduler</groupId>
            <artifactId>quartz</artifactId>
            <version>2.2.1</version>
        </dependency>
        <dependency>
            <groupId>org.quartz-scheduler</groupId>
            <artifactId>quartz-jobs</artifactId>
            <version>2.2.1</version>
        </dependency>
 

2.2建立定時任務類

import org.quartz.Job;
import org.quartz.JobExecutionContext;
import org.quartz.JobExecutionException;
import java.util.Date;

public class MyJob implements Job {

    @Override
    public void execute(JobExecutionContext jobExecutionContext) throws JobExecutionException {
        System.out.println("========quartz 測試=========="+new Date());
    }
}
 

2.3建立配置類

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.quartz.CronTriggerFactoryBean;
import org.springframework.scheduling.quartz.JobDetailFactoryBean;
import org.springframework.scheduling.quartz.SchedulerFactoryBean;
import org.springframework.scheduling.quartz.SimpleTriggerFactoryBean;

@Configuration
public class QuartzConfiguration {

    /**
     *  Job 工廠
     * @return
     */
    @Bean
    public JobDetailFactoryBean jobDetailFactoryBean() {
        JobDetailFactoryBean factory = new JobDetailFactoryBean();
        factory.setJobClass(MyJob.class);
        return factory;
    }

    /**
     *  Trigger 工廠
     * @return
     */
    @Bean
    public SimpleTriggerFactoryBean simpleTriggerFactoryBean(JobDetailFactoryBean jobDetailFactory) {
        SimpleTriggerFactoryBean factory = new SimpleTriggerFactoryBean();
        factory.setJobDetail(jobDetailFactory.getObject());
        // 執行間隔時間
        factory.setRepeatInterval(5000);
        // 重複執行次數
        factory.setRepeatCount(3);
        return factory;
    }

    /**
     *  Trigger 工廠
     * @return
     */
    @Bean
    public CronTriggerFactoryBean cronTriggerFactoryBean(JobDetailFactoryBean jobDetailFactory) {
        CronTriggerFactoryBean factory = new CronTriggerFactoryBean();
        factory.setJobDetail(jobDetailFactory.getObject());
        factory.setCronExpression("0/5 * * * * ?");
        return factory;
    }



    @Bean
    public SchedulerFactoryBean schedulerFactoryBean(CronTriggerFactoryBean cronTriggerFactory){
        SchedulerFactoryBean factory = new SchedulerFactoryBean();
        factory.setTriggers(cronTriggerFactory.getObject());
        return factory;
    }
}

同樣地，需要在 Spring Boot 的啟動類上新增 @EnableScheduling 後，啟動專案即可。

測試結果：

2.4依賴注入問題

實際開發中，任務類需要注入業務元件來執行定時任務，如下：

public class MyJob implements Job {
    @Autowired
    private UserDao userDao;
    @Override
    public void execute(JobExecutionContext jobExecutionContext) throws JobExecutionException {
        //新增
        User user1 = new User();
        user1.setuName("李四");
        int i = userDao.insertUser(user1);
        System.out.println(i);
        //查詢
        User user = userDao.getUserById(1);
        System.out.println(user);
    }
}

但是MyJob 生命週期並沒有被 Spring 容器管理，因此無法注入 UserService，當定時器執行任務時會報空指標異常。

解決方案：

自定義任務工廠，重寫建立任務例項的方法：

import org.quartz.spi.TriggerFiredBundle;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.config.AutowireCapableBeanFactory;
import org.springframework.scheduling.quartz.AdaptableJobFactory;
import org.springframework.stereotype.Component;

@Component("customAdaptableJobFactory")
public class CustomAdaptableJobFactory extends AdaptableJobFactory {

    @Autowired
    private AutowireCapableBeanFactory autowireCapableBeanFactory;

    @Override
    protected Object createJobInstance(TriggerFiredBundle bundle) throws Exception {
        Object object = super.createJobInstance(bundle);
        // 將任務例項納入 Spring 容器中
        this.autowireCapableBeanFactory.autowireBean(object);
        return object;
    }
}

修改QuartzConfiguration類 的 Scheduler 實現：

原：

@Bean
    public SchedulerFactoryBean schedulerFactoryBean(CronTriggerFactoryBean cronTriggerFactory){
        SchedulerFactoryBean factory = new SchedulerFactoryBean();
        factory.setTriggers(cronTriggerFactory.getObject());
        return factory;
    }

改：

@Bean
public SchedulerFactoryBean schedulerFactoryBean(CronTriggerFactoryBean cronTriggerFactory,CustomAdaptableJobFactory customAdaptableJobFactory){
    SchedulerFactoryBean factory = new SchedulerFactoryBean();
    factory.setTriggers(cronTriggerFactory.getObject());
    factory.setJobFactory(customAdaptableJobFactory);
    return factory;
}

測試結果：