Spring---ApplicationContext的事件机制

事件源：ApplicationContext。publishEvent()方法：用于主动触发容器事件。

事件：ApplicationEvent类,容器事件，必须由ApplicationContext发布。

事件监听器：ApplicationListener接口，可由容器中任何监听器Bean担任。onApplicationEvent(ApplicationEvent event)：每当容器内发生任何事件时，此方法都被触发

容器事件类需继承ApplicationEvent类，容器事件的监听器类需实现ApplicationListener接口。

下面给出一个例子

1.首先定义一个EmailEvent类，继承ApplicationEvent类

public class EmailEvent extends ApplicationEvent {
    private String address;
    private String text;

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

    public EmailEvent(Object source, String address, String text) {
        super(source);
        this.address = address;
        this.text = text;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getText() {
        return text;
    }

    public void setText(String text) {
        this.text = text;
    }
}

2，定义一个EmailNotifier类，实现ApplicationListener接口，并复写onApplicationEvent()方法

public class EmailNotifier implements ApplicationListener {
    @Override
    public void onApplicationEvent(ApplicationEvent applicationEvent) {
        if (applicationEvent instanceof EmailEvent){
            EmailEvent emailEvent = (EmailEvent) applicationEvent;
            System.out.println("需要发送邮件的接收地址： " + emailEvent.getAddress());
            System.out.println("需要发送邮件的邮件正文： " + emailEvent.getText());
        }else {
            System.out.println("容器本身的事件： " + applicationEvent);
        }
    }
}

3.将监听器配置在容器中

<bean class="org.spring.listener.EmailNotifier"/>

4.编写主程序main

public class SpringTest {
    public static void main(String[] args){
        ApplicationContext ctx = new ClassPathXmlApplicationContext("spring-config.xml");
//        EmailEvent ele = new EmailEvent("hello","[email protected]","this is a test");
//        ctx.publishEvent(ele);
    }
}

程序到此结束，运行结果如下：

容器本身的事件： org.springframework.context.event.ContextRefreshedEvent[source=org.springframework.context.support.ClassPathXmlApplicationContext@b81eda8: startup date [Thu Dec 04 20:20:52 CST 2014]; root of context hierarchy]

若取消main中的注释，即，使用publishEvent()来触发事件，运行结果如下：

容器本身的事件： org.springframework.context.event.ContextRefreshedEvent[source=org.springframework.context.support.ClassPathXmlApplicationContext@b81eda8: startup date [Thu Dec 04 20:24:03 CST 2014]; root of context hierarchy]
需要发送邮件的接收地址： [email protected]
需要发送邮件的邮件正文： this is a test