ObservableMetadataProvider.java

/*
 * Copyright [2006] [University Corporation for Advanced Internet Development, Inc.]
 *
 * 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.opensaml.saml2.metadata.provider;

import java.util.List;

/**
 * A metadata provider that provides event notification to observers. This may be used, for example, to signal an update
 * of an internal cache of metadata allowing other subsystems to perform some action based on that.
 * 
 */
public interface ObservableMetadataProvider extends MetadataProvider {

    /**
     * Gets the list of observers for the provider. New observers may be added to the list or old ones removed.
     * 
     * @return the list of observers
     */
    public List<Observer> getObservers();

    /**
     * An observer of metadata provider changes.
     * 
     * <strong>NOTE:</strong> The metadata provider that has changed is passed in to the
     * {@link #onEvent(MetadataProvider)} method. Observers should <strong>NOT</strong> keep a reference to this
     * provider as this may prevent proper garbage collection.
     */
    public interface Observer {

        /**
         * Called when a provider signals an event has occured.
         * 
         * @param provider the provider being observed
         */
        public void onEvent(MetadataProvider provider);
    }
}