SpringBoot 事件監(jiān)聽的 4 種實(shí)現(xiàn)方式

1. 手工向ApplicationContext中添加監(jiān)聽器
2. 將監(jiān)聽器裝載入spring容器
3. 在application.properties中配置監(jiān)聽器
4. 通過@EventListener注解實(shí)現(xiàn)事件監(jiān)聽

講到事件監(jiān)聽，這里我們說下自定義事件和自定義監(jiān)聽器類的實(shí)現(xiàn)方式：

• 自定義事件：繼承自ApplicationEvent抽象類，然后定義自己的構(gòu)造器
• 自定義監(jiān)聽：實(shí)現(xiàn)ApplicationListener接口，然后實(shí)現(xiàn)onApplicationEvent方法

下面講下4種事件監(jiān)聽的具體實(shí)現(xiàn)

方式1

首先創(chuàng)建MyListener1類

public?class?MyListener1?implements?ApplicationListener<MyEvent>
{
?Logger?logger?=?Logger.getLogger(MyListener1.class);
?
?public?void?onApplicationEvent(MyEvent?event)
?{
??logger.info(String.format("%s監(jiān)聽到事件源：%s.",?MyListener1.class.getName(),?event.getSource()));
?}
}

然后在springboot應(yīng)用啟動類中獲取ConfigurableApplicationContext上下文，裝載監(jiān)聽

@SpringBootApplication
public?class?LisenterApplication
{
?public?static?void?main(String[]?args)
?{
??ConfigurableApplicationContext?context?=?SpringApplication.run(LisenterApplication.class,?args);
??//裝載監(jiān)聽
??context.addApplicationListener(new?MyListener1());
?}
}

方式2

創(chuàng)建MyListener2類，并使用@Component注解將該類裝載入spring容器中

@Component
public?class?MyListener2?implements?ApplicationListener<MyEvent>
{
?Logger?logger?=?Logger.getLogger(MyListener2.class);
?
?public?void?onApplicationEvent(MyEvent?event)
?{
??logger.info(String.format("%s監(jiān)聽到事件源：%s.",?MyListener2.class.getName(),?event.getSource()));
?}
}

方式3

首先創(chuàng)建MyListener3類

public?class?MyListener3?implements?ApplicationListener<MyEvent>
{
?Logger?logger?=?Logger.getLogger(MyListener3.class);
?
?public?void?onApplicationEvent(MyEvent?event)
?{
??logger.info(String.format("%s監(jiān)聽到事件源：%s.",?MyListener3.class.getName(),?event.getSource()));
?}
}

然后在application.properties中配置監(jiān)聽

context.listener.classes=com.listener.MyListener3

方式4

創(chuàng)建MyListener4類，該類無需實(shí)現(xiàn)ApplicationListener接口，使用@EventListener裝飾具體方法

@Component
public?class?MyListener4
{
?Logger?logger?=?Logger.getLogger(MyListener4.class);
?
?@EventListener
?public?void?listener(MyEvent?event)
?{
??logger.info(String.format("%s監(jiān)聽到事件源：%s.",?MyListener4.class.getName(),?event.getSource()));
?}
}

自定義事件代碼如下：

@SuppressWarnings("serial")
public?class?MyEvent?extends?ApplicationEvent
{
?public?MyEvent(Object?source)
?{
??super(source);
?}
}

進(jìn)行測試(在啟動類中加入發(fā)布事件的邏輯)：

@SpringBootApplication
public?class?LisenterApplication
{
?public?static?void?main(String[]?args)
?{
??ConfigurableApplicationContext?context?=?SpringApplication.run(LisenterApplication.class,?args);
??//裝載事件
??context.addApplicationListener(new?MyListener1());
??//發(fā)布事件
??context.publishEvent(new?MyEvent("測試事件."));
?}
}

啟動后，日志打印如下：

2018-06-15?10:51:20.198??INFO?4628?---?[?????????? main] com.listener.MyListener3 ????????????????: com.listener.MyListener3監(jiān)聽到事件源：測試事件..
2018-06-15?10:51:20.198??INFO?4628?---?[?????????? main] com.listener.MyListener4 ????????????????: com.listener.MyListener4監(jiān)聽到事件源：測試事件..
2018-06-15?10:51:20.199??INFO?4628?---?[?????????? main] com.listener.MyListener2 ????????????????: com.listener.MyListener2監(jiān)聽到事件源：測試事件..
2018-06-15?10:51:20.199??INFO?4628?---?[?????????? main] com.listener.MyListener1 ????????????????: com.listener.MyListener1監(jiān)聽到事件源：測試事件..

由日志打印可以看出，SpringBoot四種事件的實(shí)現(xiàn)方式監(jiān)聽是有序的

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