Spring源码-ApplicationListener基于事件的订阅者发布者模式

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如何使用

spring容器自身提供了基于事件的订阅者发布者模式，即ApplicationListener，它能支持一些系统事件具体见ApplicationEvent的子类，同时也支持我们自定义事件使用方法如下

容器自身的事件，如：ApplicationContextEvent,我们想获取一个全局变量ApplicationContext（代码仅供参考）

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@Component
public class ContextRefreshAppliationListener implements ApplicationListener<ApplicationContextEvent> {

    public static ApplicationContextEvent applicationContext;

    //触发 application.pulish(new ContextRefreshedEvent())
    @Override
    public void onApplicationEvent(ContextRefreshedEvent event) {
        //容器启动后在某些节点会发送事件，我们只需要实现onApplicationEvent即可。
        applicationContext=event.getApplicationContext();
    }
}

自定义事件：

  1. 定义事件，事件继承自ApplicationEvent
  2. 实现该事件的AppliationListener
  3. 在程序某个时间点触发applicationContext.publishEvent方法
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public class CoustomEvent extends ApplicationEvent {
    private String name;
    private String eventType;
    private String summary;

    public CoustomEvent(Object source, String name, String eventType, String summary) {
        this(source);
        this.name = name;
        this.eventType = eventType;
        this.summary = summary;
    }

    public CoustomEvent(Object source) {
        super(source);
    }
}

@Component
public class CoustomAppliationListener implements ApplicationListener<CoustomEvent> {

    //触发 application.pulish(new ContextRefreshedEvent())
    @Override
    public void onApplicationEvent(CoustomEvent event) {
        System.out.println(event.getName() + " eventType:" + event.getEventType() + " summary:" + event.getSummary() + " in time:" + event.getTimestamp());
    }
}

//触发
applicationContext.publishEvent(new CoustomEvent("source","liuhao","sendEmail"," dest liu67224657@qq.com"));

原理

tbd