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;
    @Nullable
    private 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;
    }

    @Override
    public int getOrder() {
        return (this.delegate instanceof Ordered ? ((Ordered) this.delegate).getOrder() : Ordered.LOWEST_PRECEDENCE);
    }

    @Override
    public 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 {

    @Autowired
    private ApplicationEventMulticaster eventMulticaster;
    @Autowired
    private 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

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