關於Spring Task 觸發時同時執行兩次的問題

say-event-provider.xml

<!-- lang: xml -->
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:dubbo="http://code.alibabatech.com/schema/dubbo"
xmlns:jdbc="http://www.springframework.org/schema/jdbc" 
xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:task="http://www.springframework.org/schema/task" 
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd
http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-3.2.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.2.xsd
http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task-3.2.xsd
http://code.alibabatech.com/schema/dubbo http://code.alibabatech.com/schema/dubbo/dubbo.xsd">

<dubbo:registry address="zookeeper://127.0.0.1:2181" />

<bean id="eventService" class="com.say.event.provider.EventServiceImpl" />
<dubbo:service interface="com.say.event.EventService" ref="eventService" />
<bean id="eventMomentService" class="com.say.event.provider.EventMomentServiceImpl" />
<dubbo:service interface="com.say.event.EventMomentService" ref="eventMomentService" />

<dubbo:reference id="pushService" interface="com.say.user.PushService" />

<context:component-scan base-package="com.say.event"/>
<task:annotation-driven/>.....

xxx.java

<!-- lang: java -->
@Component
@Transactional
public class EventServiceImpl implements EventService {
final static Logger logger = Logger.getLogger(EventServiceImpl.class);
    ....
@Scheduled(cron="0 0/1 * * * ?")   //每分鐘觸發一次 
public void test(){
	System.err.println(this +" === "+ new Date() +" === "+ Thread.currentThread().getId() +" === "+ Thread.currentThread().getName() );
}

執行結果:

上圖中看到在同一時間點執行了兩次。 同時，查以經過劃紅色下劃紅的結果： com.say.event.provider.EventServiceImpl**@20fc40ae** com.say.event.provider.EventServiceImpl**@19aa5882** 能夠看出他們不是同一個實例，因爲能夠看出是EventServiceImpl 的兩個不一樣實例的*test()*方法分別被執行了一次，加來共爲兩次。

爲何執行了兩次, 或者說什麼會產兩個實例？，Spring Bean的scope 默承認是singleton的哦...

緣由就出在say-event-provider.xml的

<!-- lang: xml -->
<bean id="eventService" class="com.say.event.provider.EventServiceImpl" />

和 xxx.java的第一行代碼 @Component註解。它們兩個會使用Spring 在初始化的過程當中分別產生一個EventServiceImpl的實例。因此致使以上的結果。