org.springframework.boot.context.config.DelegatingApplicationListener Maven / Gradle / Ivy
/*
* Copyright 2012-2017 the original author or authors.
*
* Licensed 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
*
* https://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.springframework.boot.context.config;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import org.springframework.beans.BeanUtils;
import org.springframework.boot.context.event.ApplicationEnvironmentPreparedEvent;
import org.springframework.context.ApplicationContextException;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.context.event.SimpleApplicationEventMulticaster;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.AnnotationAwareOrderComparator;
import org.springframework.core.env.ConfigurableEnvironment;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.StringUtils;
/**
* {@link ApplicationListener} that delegates to other listeners that are specified under
* a {@literal context.listener.classes} environment property.
*
* @author Dave Syer
* @author Phillip Webb
*/
public class DelegatingApplicationListener
implements ApplicationListener, Ordered {
// NOTE: Similar to org.springframework.web.context.ContextLoader
private static final String PROPERTY_NAME = "context.listener.classes";
private int order = 0;
private SimpleApplicationEventMulticaster multicaster;
@Override
public void onApplicationEvent(ApplicationEvent event) {
if (event instanceof ApplicationEnvironmentPreparedEvent) {
List> delegates = getListeners(
((ApplicationEnvironmentPreparedEvent) event).getEnvironment());
if (delegates.isEmpty()) {
return;
}
this.multicaster = new SimpleApplicationEventMulticaster();
for (ApplicationListener listener : delegates) {
this.multicaster.addApplicationListener(listener);
}
}
if (this.multicaster != null) {
this.multicaster.multicastEvent(event);
}
}
@SuppressWarnings("unchecked")
private List> getListeners(
ConfigurableEnvironment environment) {
if (environment == null) {
return Collections.emptyList();
}
String classNames = environment.getProperty(PROPERTY_NAME);
List> listeners = new ArrayList<>();
if (StringUtils.hasLength(classNames)) {
for (String className : StringUtils.commaDelimitedListToSet(classNames)) {
try {
Class clazz = ClassUtils.forName(className,
ClassUtils.getDefaultClassLoader());
Assert.isAssignable(ApplicationListener.class, clazz, "class ["
+ className + "] must implement ApplicationListener");
listeners.add((ApplicationListener) BeanUtils
.instantiateClass(clazz));
}
catch (Exception ex) {
throw new ApplicationContextException(
"Failed to load context listener class [" + className + "]",
ex);
}
}
}
AnnotationAwareOrderComparator.sort(listeners);
return listeners;
}
public void setOrder(int order) {
this.order = order;
}
@Override
public int getOrder() {
return this.order;
}
}