spring 事件(Application Event)

spring 事件为bean 与 bean之间传递消息。一个bean处理完了希望其余一个接着处理.这时我们就需要其余的一个bean监听当前bean所发送的事件.

 

spring事件使用步骤如下:

1.先自定义事件：你的事件需要继承 ApplicationEvent

2.定义事件监听器: 需要实现 ApplicationListener

3.使用容器对事件进行发布

 

以下例子是场景是注册的时候发送邮件的一个场景:

先定义事件：

package com.example.springdemo.event;

import org.springframework.context.ApplicationEvent;

public class EmailEvent extends ApplicationEvent {

    private static final long serialVersionUID = -7387041334869267078L;

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

    private String msg;
    private String email;

    public String getMsg() {
        return msg;
    }

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

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

}

然后定义事件监听器:

package com.example.springdemo.event;

import org.springframework.context.ApplicationListener;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Component;

@Component
public class EmailListener implements ApplicationListener<EmailEvent>{
    //使用注解@Async支持 这样不仅可以支持通过调用，也支持异步调用，非常的灵活
    @Async
    @Override
    public void onApplicationEvent(EmailEvent event) {
        System.out.println("收到了邮件:" + event.getEmail() + ";内容：" + event.getMsg());
    }

}

上述代码也可用@EventListener替换，无需实现类，可随便定义方法名，如：

@Component
public class EmailListener{
    @EventListener
    public void receive(EmailEvent event) {
        System.out.println("收到了邮件:" + event.getEmail() + ";内容：" + event.getMsg());
    }
}

再次使用容器对事件进行发布:

package com.example.springdemo.event;

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

@Component
public class EmailPublisher {
    @Autowired
    private ApplicationContext applicationContext;
    
    public void publish(String email, String msg) {
        applicationContext.publishEvent(new EmailEvent(this, msg, email));
    }
}

最后就是测试了:

package com.example.springdemo.event;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ComponentScan("com.example.springdemo.event")
public class EmailConfig {

}

package com.example.springdemo.event;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class SpringEventTest {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext context=new AnnotationConfigApplicationContext(EmailConfig.class);
        EmailPublisher publisher = context.getBean(EmailPublisher.class);
        publisher.publish("张三", "雷猴啊");
        context.close();
    }
}

结果:

19:35:42.535 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Returning cached instance of singleton bean 'emailPublisher'
19:35:42.536 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Returning cached instance of singleton bean 'emailListener'
收到了邮件:张三;内容：雷猴啊
19:35:42.537 [main] INFO org.springframework.context.annotation.AnnotationConfigApplicationContext - Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@5ecddf8f: startup date [Mon Jan 21 19:35:42 CST 2019]; root of context hierarchy
19:35:42.537 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Returning cached instance of singleton bean 'lifecycleProcessor'
19:35:42.537 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Destroying singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@77cd7a0: defining beans [org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,org.springframework.context.event.internalEventListenerProcessor,org.springframework.context.event.internalEventListenerFactory,emailConfig,emailListener,emailPublisher]; root of factory hierarchy