SpringBoot监听器之发布订阅、观察者模式

SpringBoot监听器使用
实现方式有2种：实现ApplicationListener 接口；添加@EventListener 注解。
必须要的角色：
1、事件（event）可以封装和传递监听器中要处理的参数，如对象或字符串，并作为监听器中监听的目标。
2、监听器（listener）具体根据事件发生的业务处理模块，这里可以接收处理事件中封装的对象或字符串。
3、事件发布者（publisher）事件发生的触发者。

接口实现：
自定义事件需要继承Spring的ApplicationEvent
自定义监听器需要实现ApplicationListener
自定义事件发布需要自动注入了ApplicationEventPublisher
注解实现：
自定义事件需要继承Spring的ApplicationEvent
自定义监听器，在自定义的方法上添加@EventListener
自定义事件发布需要自动注入了ApplicationEventPublisher

参考：
https://segmentfault.com/a/1190000039097608

MyEvent

import org.springframework.context.ApplicationEvent;

public class MyEvent extends ApplicationEvent {
    private String msg;

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

    public MyEvent(Object source, String msg) {
        super(source);
        this.msg = msg;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }
}

MyEventTwo

import org.springframework.context.ApplicationEvent;

public class MyEventTwo extends ApplicationEvent {
    private String msg;

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

    public MyEventTwo(Object source, String msg) {
        super(source);
        this.msg = msg;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }
}

MyAnnotationListener

import org.springframework.context.ApplicationEvent;
import org.springframework.context.event.EventListener;
import org.springframework.stereotype.Component;

@Component
public class MyAnnotationListener {
    @EventListener(classes={MyEvent.class,MyEventTwo.class})
    public void listener(ApplicationEvent applicationEvent){
        if(applicationEvent instanceof MyEvent){
            System.out.println("MyAnnotationListener - MyEvent:"+((MyEvent) applicationEvent).getMsg());
        }

        if(applicationEvent instanceof MyEventTwo){
            System.out.println("MyAnnotationListener - MyEventTwo:"+((MyEventTwo) applicationEvent).getMsg());
        }

    }

    @EventListener
    public void listenerTestOne(MyEvent myEvent){
        System.out.println("listenerTestOne"+myEvent.getMsg());
    }

    @EventListener
    public void listenerTestTwo(MyEventTwo myEventTwo){
        System.out.println("listenerTestTwo"+myEventTwo.getMsg());
    }
}

MyEventPubLisher

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationEventPublisher;
import org.springframework.stereotype.Component;

@Component
public class MyEventPubLisher {
    @Autowired
    private ApplicationEventPublisher applicationEventPublisher;

    public void pushListener(String msg) {
        applicationEventPublisher.publishEvent(new MyEvent(this, msg));
    }

    public void pushListenerTwo(String msg) {
        applicationEventPublisher.publishEvent(new MyEventTwo(this, msg));
    }

}

ObserverController 测试接口

import com.tech.elasticsearch.observer.MyEventPubLisher;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/observer")
public class ObserverController {
    @Autowired
    private MyEventPubLisher myEventPubLisher;

    @GetMapping("/publish1")
    public void publisher(String msg){
        myEventPubLisher.pushListener(msg);
    }

    @GetMapping("/publish2")
    public void pushListenerTwo(String msg){
        myEventPubLisher.pushListenerTwo(msg);
    }
}

说明：在MyAnnotationListener类中
如果参数为ApplicationEvent applicationEvent
@EventListener(classes={MyEvent.class,MyEventTwo.class})，则只监听这2个类
@EventListener，则监听所有继承了ApplicationEvent的类

如果参数为MyEvent myEvent或者MyEventTwo myEventTwo
@EventListener，只监听参数类型的事件