| // Copyright 2006, 2007, 2008, 2010 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.tapestry5.services; |
| |
| import org.apache.tapestry5.ioc.ObjectLocator; |
| |
| /** |
| * Manages a set of {@link org.apache.tapestry5.services.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 #fireCheckForUpdates()}. 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.tapestry5.services.InvalidationListener} that they should do the same. |
| * <p> |
| * Note that this interface has moved from module tapestry-core to tapestry-ioc, but has kept the same package (for |
| * backwards compatibility reasons). |
| * <p> |
| * A <em>weak reference</em> to the listener is kept; this ensures that registering as a listener will not prevent a |
| * listener instance from being reclaimed by the garbage collector (this is useful as proxies created by |
| * {@link ObjectLocator#proxy(Class, Class)} may register as listeners, but still be ephemeral). |
| * |
| * @since 5.1.0.0 |
| */ |
| public interface UpdateListenerHub |
| { |
| /** |
| * Adds a listener. |
| */ |
| 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.tapestry5.services.InvalidationEventHub}) when such a change occurs. |
| */ |
| void fireCheckForUpdates(); |
| } |