ApplicationListener的简单使用

ApplicationListener在Spring框架中的作用是监听并处理应用程序中的事件。
ApplicationListener接口定义了一个onApplicationEvent方法，当监听器监听到事件发布后，会执行这个方法。这使得开发者能够灵活地响应应用程序中的各种事件，实现发布-订阅模式的功能。通过这种方式，Spring框架实现了应用程序内部不同组件之间的松耦合通信，提高了系统的可扩展性和可维护性。
代码结构：

1、定义监听实体

根据发布和订阅的实体不同，进行区分不同的监听。
People

package com.dyaqi.domain;

import lombok.Getter;
import lombok.Setter;
import lombok.ToString;
import org.springframework.context.ApplicationEvent;

/**
 * @author: dongyq
 * @date: 2023/4/17 17:34
 * @since:
 * @功能描述:
 */
@Getter
@Setter
@ToString
public class People extends ApplicationEvent {
    public String name;
    public Integer age;

    public People(Object source, String name, Integer age) {
        super(source);
        this.name = name;
        this.age = age;
    }
}

User

package com.dyaqi.domain;

import lombok.Getter;
import lombok.Setter;
import lombok.ToString;
import org.springframework.context.ApplicationEvent;

/**
 * @author: dongyq
 * @date: 2023/4/17 17:34
 * @since:
 * @功能描述:
 */
@Getter
@Setter
@ToString
public class User extends ApplicationEvent {
    public String name;
    public Integer age;

    public User(Object source, String name, Integer age) {
        super(source);
        this.name = name;
        this.age = age;
    }
}

2、定义发布者

package com.dyaqi.publisher;

import com.dyaqi.domain.People;
import com.dyaqi.domain.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationEventPublisher;
import org.springframework.stereotype.Component;

/**
 * @author: dongyq
 * @date: 2023/4/17 17:40
 * @since:
 * @功能描述:
 */
@Component
public class Publisher {

    @Autowired
    private ApplicationEventPublisher applicationEventPublisher;

    public void publis() {
        System.out.println("发布事件");
        applicationEventPublisher.publishEvent(new People(this,"张三", 29));
        applicationEventPublisher.publishEvent(new User(this,"李四", 18));
    }
}

3、定义订阅者

Listener1 监听 People

package com.dyaqi.listener;

import com.dyaqi.domain.People;
import org.springframework.context.ApplicationListener;
import org.springframework.stereotype.Component;

/**
 * @author: dongyq
 * @date: 2023/4/17 17:37
 * @since:
 * @功能描述:
 */
@Component
public class Listener1 implements ApplicationListener<People> {
    @Override
    public void onApplicationEvent(People people) {
        System.out.println("Listener1 监听到事件");
        System.out.println(people.toString());
    }
}

Listener2监听 User

package com.dyaqi.listener;

import com.dyaqi.domain.People;
import com.dyaqi.domain.User;
import org.springframework.context.ApplicationListener;
import org.springframework.stereotype.Component;

/**
 * @author: dongyq
 * @date: 2023/4/17 17:37
 * @since:
 * @功能描述:
 */
@Component
public class Listener2 implements ApplicationListener<User> {
    @Override
    public void onApplicationEvent(User user) {
        System.out.println("Listener2 监听到事件");
        System.out.println(user.toString());
    }
}

使用注解监听

package com.dyaqi.listener;

import com.dyaqi.domain.User;
import org.springframework.context.ApplicationListener;
import org.springframework.context.event.EventListener;
import org.springframework.stereotype.Component;

/**
 * @author: dongyq
 * @date: 2023/4/17 17:37
 * @since:
 * @功能描述:
 */
@Component
public class Listener3 {
    @EventListener
    public void onApplicationEvent(User user) {
        System.out.println("Listener3 监听到事件");
        System.out.println(user.toString());
    }
}