Spring学习系列之事件处理机制使用及实现

// 定制事件
public class InitEvent extends ApplicationEvent {

    public String getData() {
        return data;
    }

    public void setData(String data) {
        this.data = data;
    }

    public String data;

    /**
     * Create a new ApplicationEvent.
     *
     * @param source the component that published the event (never {@code null})
     */
    public InitEvent(Object source) {
        super(source);
    }

    public InitEvent(Object source, String data) {
        super(source);
        this.data = data;
    }
}

// 监听事件
public class InitEventListener implements ApplicationListener<InitEvent> {
    @Override
    public void onApplicationEvent(InitEvent event) {
        System.out.println("接收到initevent：" + event.getData());
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:context="http://www.springframework.org/schema/context"
	   xmlns:task="http://www.springframework.org/schema/task" 
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
            http://www.springframework.org/schema/beans/spring-beans.xsd
            http://www.springframework.org/schema/context
            http://www.springframework.org/schema/context/spring-context-4.1.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd 
			http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task-3.0.xsd">

    <task:executor id="executor" pool-size="10" />  
	<!-- 名字必须是applicationEventMulticaster和messageSource是一样的，默认找这个名字的对象 -->  
	<!-- 名字必须是applicationEventMulticaster，因为AbstractApplicationContext默认找个 -->  
	<!-- 如果找不到就new一个，但不是异步调用而是同步调用 -->  
	<bean id="applicationEventMulticaster" class="org.springframework.context.event.SimpleApplicationEventMulticaster">  
		<!-- 注入任务执行器 这样就实现了异步调用（缺点是全局的，要么全部异步，要么全部同步（删除这个属性即是同步））  -->  
		<property name="taskExecutor" ref="executor"/>  
	</bean> 

	<bean class="mytests.events.InitEventListener"/>
</beans>

// 这里直接通过ApplicationContext发布事件，还可以通过实现接口ApplicationEventPublisherAware获取
// ApplicationEventPublisher对象来发布事件  
public class PublishEvent {
    public static void main(String[] args) {
        FileSystemXmlApplicationContext context =
                new FileSystemXmlApplicationContext("beans.xml");
        context.publishEvent(new InitEvent("testEvent", "event"));
        context.close();
    }
}

执行结果：  
接收到initevent：event

public class PublishEvent {
    public static void main(String[] args) {
        FileSystemXmlApplicationContext context =
                new FileSystemXmlApplicationContext("C:\\Users\\michael\\Desktop\\beans.xml");
        context.publishEvent(new InitEvent("testEvent", "event"));
        context.close();
    }
}

public abstract class AbstractApplicationContext extends DefaultResourceLoader
		implements ConfigurableApplicationContext, DisposableBean {

    public void publishEvent(ApplicationEvent event) {
		Assert.notNull(event, "Event must not be null");
		if (logger.isTraceEnabled()) {
			logger.trace("Publishing event in " + getDisplayName() + ": " + event);
		}
        // 通过内置的ApplicationEventMulticaster发布事件，这里实际是SimpleApplicationEventMulticaster类对象
		getApplicationEventMulticaster().multicastEvent(event);
		if (this.parent != null) {
			this.parent.publishEvent(event);
		}
	}
}

public class SimpleApplicationEventMulticaster extends AbstractApplicationEventMulticaster {

    private Executor taskExecutor; // 使用线程池异步调用监听器的监听方法 
    
    public void multicastEvent(final ApplicationEvent event) {
        // 通过getApplicationListeners获取关注这个事件的所有监听器，挨个进行通知
		for (final ApplicationListener listener : getApplicationListeners(event)) {
			Executor executor = getTaskExecutor();
            // 如果指定了线程池
			if (executor != null) {
				executor.execute(new Runnable() {
					public void run() {
						listener.onApplicationEvent(event);
					}
				});
			}
			else { // 同步调用监听器监听方法
				listener.onApplicationEvent(event);
			}
		}
	}
}