Spring中实现自定义事件

原理：

1. 通过扩展ApplicationEvent,创建一个事件类CustomEvent。这个类必须定义一个默认的构造函数，它应该从ApplicationEvent类中继承的构造函数。
2. 一旦定义事件类，你可以从任何类中发布它，假定EventClassPublisher实现了ApplicationEventPublisherAware。你还需要在XML配置文件中声明这个类作为一个bean，之所以容器可以识别bean作为事件发布者，是因为它实现了ApplicationEventPublisherAware接口。
3. 发布的事件可以在一个类中被处理，假定EventClassHandler实现了ApplicationListener接口，而且实现了自定义事件的onApplicationEvent方法。

例子：

pom.xml：

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.jsoft.testspring</groupId>
  <artifactId>testcustomevent</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>testcustomevent</name>
  <url>http://maven.apache.org</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    
    <!-- Spring Core -->
    <!-- http://mvnrepository.com/artifact/org.springframework/spring-core -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>4.1.4.RELEASE</version>
    </dependency>
     
    <!-- Spring Context -->
    <!-- http://mvnrepository.com/artifact/org.springframework/spring-context -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>4.1.4.RELEASE</version>
    </dependency>
    
  </dependencies>
</project>

CustomEvent.java：

package com.jsoft.testspring.testcustomevent;

import org.springframework.context.ApplicationEvent;

public class CustomEvent extends ApplicationEvent {

    public CustomEvent(Object source) {
        super(source);
        // TODO Auto-generated constructor stub
    }
    
    public String toString(){
        return "My Custom Event";
    }

}

CustomEventPublisher.java：

package com.jsoft.testspring.testcustomevent;

import org.springframework.context.ApplicationEventPublisher;
import org.springframework.context.ApplicationEventPublisherAware;

public class CustomEventPublisher implements ApplicationEventPublisherAware {

    private ApplicationEventPublisher publisher;
    
    @Override
    public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
        // TODO Auto-generated method stub
        this.publisher = applicationEventPublisher;
    }
    
    public void publish(){
        CustomEvent ce = new CustomEvent(this);
        publisher.publishEvent(ce);
    }

}

CustomEventHandler.java：

package com.jsoft.testspring.testcustomevent;

import org.springframework.context.ApplicationListener;

public class CustomEventHandler implements ApplicationListener<CustomEvent> {

    @Override
    public void onApplicationEvent(CustomEvent event) {
        // TODO Auto-generated method stub
        System.out.println(event.toString());
    }

}

beans.xml：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
                        http://www.springframework.org/schema/beans/spring-beans.xsd">
        
    <bean id="customEventHandler" class="com.jsoft.testspring.testcustomevent.CustomEventHandler"></bean>
    
    <bean id="customEventPublisher" class="com.jsoft.testspring.testcustomevent.CustomEventPublisher"></bean>
</beans>

App.java：

package com.jsoft.testspring.testcustomevent;

import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * Hello world!
 *
 */
public class App 
{
    public static void main( String[] args )
    {
        ConfigurableApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
        CustomEventPublisher publisher = (CustomEventPublisher)context.getBean("customEventPublisher");
        publisher.publish();
        publisher.publish();
    }
}

测试结果：

总结：

此实例中主要理解为：1、事件发布；2、事件监听；3、实现事件处理。

beans中主要是事件处理类的初始化和事件发布类的初始化。

测试工程：https://github.com/easonjim/5_java_example/tree/master/springtest/test15