// Copyright 2006, 2007 The Apache Software Foundation
//
// 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.apache.tapestry.internal.services;
import org.apache.tapestry.internal.events.UpdateListener;
/**
* Manages a set of {@link org.apache.tapestry.internal.events.UpdateListener}s. Periodically (say, every
* request during development, or every minute or so during production), request processing is
* locked down so that only a single thread is active, and the active thread invokes
* {@link #fireUpdateEvent()}. Various services that are dependent on external resource files (such
* as classes or template files) can check to see if any file they've used has changed. If so, the
* service can invalidate its internal cache, or notify other services (typically via
* {@link org.apache.tapestry.internal.events.InvalidationListener} that they should do the same.
*
*
* @see org.apache.tapestry.internal.util.URLChangeTracker
*/
public interface UpdateListenerHub
{
void addUpdateListener(UpdateListener listener);
/**
* Invoked periodically to allow services to check if underlying state has changed. For example,
* a template file may have changed. Listeners will typically notify applicable listeners of
* their own (they usually implement
* {@link org.apache.tapestry.internal.event.InvalidationEventHub}) when such a change occurs.
*/
void fireUpdateEvent();
}
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