/*
* Copyright 2002-2009 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
*
* 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.springframework.context.event;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.core.Ordered;
/**
* {@link org.springframework.context.ApplicationListener} decorator that filters
* events from a specified event source, invoking its delegate listener for
* matching {@link org.springframework.context.ApplicationEvent} objects only.
*
* <p>Can also be used as base class, overriding the {@link #onApplicationEventInternal}
* method instead of specifying a delegate listener.
*
* @author Juergen Hoeller
* @since 2.0.5
*/
public class SourceFilteringListener implements SmartApplicationListener {
private final Object source;
private SmartApplicationListener delegate;
/**
* Create a SourceFilteringListener for the given event source.
* @param source the event source that this listener filters for,
* only processing events from this source
* @param delegate the delegate listener to invoke with event
* from the specified source
*/
public SourceFilteringListener(Object source, ApplicationListener delegate) {
this.source = source;
this.delegate = (delegate instanceof SmartApplicationListener ?
(SmartApplicationListener) delegate : new GenericApplicationListenerAdapter(delegate));
}
/**
* Create a SourceFilteringListener for the given event source,
* expecting subclasses to override the {@link #onApplicationEventInternal}
* method (instead of specifying a delegate listener).
* @param source the event source that this listener filters for,
* only processing events from this source
*/
protected SourceFilteringListener(Object source) {
this.source = source;
}
public void onApplicationEvent(ApplicationEvent event) {
if (event.getSource() == this.source) {
onApplicationEventInternal(event);
}
}
public boolean supportsEventType(Class<? extends ApplicationEvent> eventType) {
return (this.delegate == null || this.delegate.supportsEventType(eventType));
}
public boolean supportsSourceType(Class<?> sourceType) {
return sourceType.isInstance(this.source);
}
public int getOrder() {
return (this.delegate != null ? this.delegate.getOrder() : Ordered.LOWEST_PRECEDENCE);
}
/**
* Actually process the event, after having filtered according to the
* desired event source already.
* <p>The default implementation invokes the specified delegate, if any.
* @param event the event to process (matching the specified source)
*/
@SuppressWarnings("unchecked")
protected void onApplicationEventInternal(ApplicationEvent event) {
if (this.delegate == null) {
throw new IllegalStateException(
"Must specify a delegate object or override the onApplicationEventInternal method");
}
this.delegate.onApplicationEvent(event);
}
}
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