java - 如何通过代码注册Spring ApplicationListener实现？

我有一个Spring ApplicationListener的实现。当在上下文xml文件中将其声明为bean或使用@Component批注时，它可以正常工作并接收事件。

但是，如果我使用ConfigurableListableBeanFactory的registerSingleton()方法通过代码手动注册它，则它不会接收事件。

我在下面添加了一些示例代码，这些示例代码描述了有效的案例和不可行的案例。

CustomEvent.java

package com.test.event;

import org.springframework.context.ApplicationEvent;

public class CustomEvent extends ApplicationEvent {

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

    public String toString() {
        return "My Custom Event";
    }
}

CustomEventPublisher.java

package com.test.event;

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

public class CustomEventPublisher implements ApplicationEventPublisherAware {

    private ApplicationEventPublisher publisher;

    public void setApplicationEventPublisher(ApplicationEventPublisher publisher) {
        this.publisher = publisher;
    }

    public void publish() {
        CustomEvent ce = new CustomEvent(this);
        publisher.publishEvent(ce);
    }
}

CustomEventHandler.java

package com.test.event;

import org.springframework.context.ApplicationListener;

public class CustomEventHandler
   implements ApplicationListener<CustomEvent>{

   public void onApplicationEvent(CustomEvent event) {
      System.out.println(event.toString());
   }

}

applicationContextWithListenerBean.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-3.0.xsd">

   <bean id="customEventHandler"
      class="com.test.event.CustomEventHandler"/>

   <bean id="customEventPublisher"
      class="com.test.event.CustomEventPublisher"/>

</beans>

applicationContextWithoutListenerBean.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-3.0.xsd">

   <bean id="customEventPublisher"
      class="com.test.event.CustomEventPublisher"/>

</beans>

MainApp.java

package com.test.event;

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

public class MainApp {
    public static void main(String[] args){

        /* The below code works fine when listener bean customEventHandler is defined in xml */

        ConfigurableApplicationContext context = new ClassPathXmlApplicationContext(
                "applicationContextWithListenerBean.xml");
        CustomEventPublisher cvp = (CustomEventPublisher) context
                .getBean("customEventPublisher");
        cvp.publish();
        context.close();

        /* The below code doesn't work when listener bean is registered through code. Is it possible to make this work? */

        ConfigurableApplicationContext context = new ClassPathXmlApplicationContext(
                "applicationContextWithoutListenerBean.xml");
        context.getBeanFactory().registerSingleton("customEventHandler",
                new CustomEventHandler());
        CustomEventPublisher cvp = (CustomEventPublisher) context
                .getBean("customEventPublisher");

        cvp.publish();
        context.close();
    }
}

无法通过代码注册ApplicationListener吗？

最佳答案

将bean注册为单例将不会使其在ApplicationEvents上被调用。

context.getBeanFactory().registerSingleton("customEventHandler",
            new CustomEventHandler());

应该更改为

context.addApplicationListener(new CustomEventHandler());

这会将ApplicationListener实现添加到ApplicationEventMulticaster中，该事件将事件发布到ApplicationListeners中