动态添加Spring的事件监听

在实际项目中，有些事件可能需要动态添加监听器，比如从配置中加载

在Spring中好像没有可以指定事件添加监听器方法，都是根据类反射得到监听的事件类型

只能自己实现一下监听器了

public class DynamicSpringEventListener implements GenericApplicationListener {private final ApplicationListener<ApplicationEvent> delegate;@Nullableprivate final ResolvableType declaredEventType;public DynamicSpringEventListener(Class<? extends ApplicationEvent> eventClass, ApplicationListener<ApplicationEvent> delegate) {Assert.notNull(delegate, "Delegate listener must not be null");this.delegate = delegate;this.declaredEventType = ResolvableType.forClass(eventClass);}public void onApplicationEvent(ApplicationEvent event) {this.delegate.onApplicationEvent(event);}public boolean supportsEventType(ResolvableType eventType) {return this.declaredEventType == null || this.declaredEventType.isAssignableFrom(eventType);}public boolean supportsSourceType(@Nullable Class<?> sourceType) {return true;}@Overridepublic int getOrder() {return (this.delegate instanceof Ordered ? ((Ordered) this.delegate).getOrder() : Ordered.LOWEST_PRECEDENCE);}@Overridepublic String getListenerId() {return (this.delegate instanceof SmartApplicationListener ? ((SmartApplicationListener) this.delegate).getListenerId() : "");}
}

使用方法

package com.test;import jakarta.annotation.PostConstruct;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationEventPublisher;
import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ApplicationEventMulticaster;
import org.springframework.context.event.EventListener;
import org.springframework.stereotype.Component;@Component
public class TestPublisher {@Autowiredprivate ApplicationEventMulticaster eventMulticaster;@Autowiredprivate ApplicationEventPublisher eventPublisher;public void addEventListener(Class<? extends ApplicationEvent> eventClass) {System.err.println("add event for class " + eventClass.getSimpleName());DynamicSpringEventListener eventListener = new DynamicSpringEventListener(eventClass, event -> {System.err.println("on test event");});eventMulticaster.addApplicationListener(eventListener);}}

　　根据需要动态添加

    @PostConstructpublic void init() {Class[] events = new Class[] {TestApplicationEvent.class};for (Class clazz : events) {addEventListener(clazz);}}