Spring 事件(2)- 自定义事件
除了内置事件,Spring中也可以使用自定义事件。
怎样使用自定义事件:
- 创建事件类 - 扩展
ApplicationEvent
类,创建事件类。 - 创建发送类 - 发送类获取
ApplicationEventPublisher
实例发送事件。 - 创建监听类 - 实现
ApplicationListener
接口,创建监听类。
事件类
事件类用于存储事件数据。下面创建一个简单的事件类。
CustomEvent.java
import org.springframework.context.ApplicationEvent;
public class CustomEvent extends ApplicationEvent {
public CustomEvent(Object source, String message) {
super(source);
}
public String toString() {
return "我是自定义事件";
}
}
发送类
发送类创建事件对象并发送。
要发送事件,这里介绍2种方法:
- 使用
@autowired
注解注入ApplicationEventPublisher
实例。
CustomEventPublisher.java
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationEventPublisher;
public class CustomEventPublisher {
@Autowired
private ApplicationEventPublisher publisher;
public void publish() {
CustomEvent event = new CustomEvent(this);
publisher.publishEvent(event);
}
}
- 发送类实现
ApplicationEventPublisherAware
接口,获取ApplicationEventPublisher
实例。
CustomEventPublisher.java
import org.springframework.context.ApplicationEventPublisher;
import org.springframework.context.ApplicationEventPublisherAware;
public class CustomEventPublisher implements ApplicationEventPublisherAware {
private ApplicationEventPublisher publisher;
// 必须重写这个方法获取ApplicationEventPublisher
public void setApplicationEventPublisher (ApplicationEventPublisher publisher){
this.publisher = publisher;
}
public void publish() {
CustomEvent event = new CustomEvent(this);
publisher.publishEvent(event);
}
}
如果发送类实现了ApplicationEventPublisherAware
接口,发送类必须声明为bean,Spring容器将其标识为事件发送者。
<bean id="customEventPublisher" class="CustomEventPublisher"/>
监听类
监听类监听事件。监听类必须实现ApplicationListener
接口,并且被定义为Bean以便Spring容器可以加载它。
beans.xml
<bean id="customEventHandler" class="CustomEventHandler"/>
CustomEventHandler.java
import org.springframework.context.ApplicationListener;
public class CustomEventHandler implements ApplicationListener<CustomEvent> {
public void onApplicationEvent(CustomEvent event) {
System.out.println("收到事件:" + event.toString());
}
}
运行
测试自定义事件。
Test.java
import org.springframework.context.ApplicationContext;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class Test {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");
CustomEventPublisher publisher = (CustomEventPublisher) context.getBean("customEventPublisher");
publisher.publish();
}
}