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OneTimeExecutionApplicationContextEventListener.java
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OneTimeExecutionApplicationContextEventListener.java
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.dubbo.config.spring.context;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ApplicationContextEvent;
import java.util.Objects;
/**
* The abstract class {@link ApplicationListener} for {@link ApplicationContextEvent} guarantees just one-time execution
* and prevents the event propagation in the hierarchical {@link ApplicationContext ApplicationContexts}
*
* @since 2.7.5
*/
abstract class OneTimeExecutionApplicationContextEventListener implements ApplicationListener, ApplicationContextAware {
private ApplicationContext applicationContext;
public final void onApplicationEvent(ApplicationEvent event) {
if (isOriginalEventSource(event) && event instanceof ApplicationContextEvent) {
onApplicationContextEvent((ApplicationContextEvent) event);
}
}
/**
* The subclass overrides this method to handle {@link ApplicationContextEvent}
*
* @param event {@link ApplicationContextEvent}
*/
protected abstract void onApplicationContextEvent(ApplicationContextEvent event);
/**
* Is original {@link ApplicationContext} as the event source
*
* @param event {@link ApplicationEvent}
* @return
*/
private boolean isOriginalEventSource(ApplicationEvent event) {
return (applicationContext == null) // Current ApplicationListener is not a Spring Bean, just was added
// into Spring's ConfigurableApplicationContext
|| Objects.equals(applicationContext, event.getSource());
}
@Override
public final void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
this.applicationContext = applicationContext;
}
public ApplicationContext getApplicationContext() {
return applicationContext;
}
}