关于Spring Task 触发时同时执行两次的问题

say-event-provider.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

@Component
@Transactional
public class EventServiceImpl implements EventService {
final static Logger logger = Logger.getLogger(EventServiceImpl.class);
    ....
@Scheduled(cron="0 0/1 * * * ?")   //每分钟触发一次 
public void test(){
    System.err.println(this +" === "+ new Date() +" === "+ Thread.currentThread().getId() +" === "+ Thread.currentThread().getName() );
}

执行结果:

上图中看到在同一时间点执行了两次。
同时，查以通过划红色下划红的结果：
com.say.event.provider.EventServiceImpl@20fc40ae
com.say.event.provider.EventServiceImpl@19aa5882
可以看出他们不是同一个实例，由于可以看出是EventServiceImpl 的两个不同实例的test()方法分别被执行了一次，加来共为两次。

为什么执行了两次, 或者说什么会产两个实例？，Spring Bean的scope 默认可是singleton的哦…

原因就出在say-event-provider.xml的

<bean id="eventService" class="com.say.event.provider.EventServiceImpl" />

和 xxx.java的第一行代码 @Component注解。它们两个会使用Spring 在初始化的过程中分别产生一个EventServiceImpl的实例。所以导致以上的结果。