/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.jackrabbit.oak.spi.commit;
import static com.google.common.base.Preconditions.checkNotNull;
import java.io.Closeable;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import org.apache.jackrabbit.oak.spi.state.NodeState;
/**
* A {@code ChangeDispatcher} instance dispatches content changes
* to registered {@link Observer}s.
* <p>
* Changes are reported by calling {@link #contentChanged(NodeState, CommitInfo)}.
* <p>
* The {@link #addObserver(Observer)} method registers an {@link Observer} for receiving
* notifications for all changes reported to this instance.
*/
public class ChangeDispatcher implements Observable, Observer {
private final CompositeObserver observers = new CompositeObserver();
@Nonnull
private NodeState root;
/**
* Create a new instance for dispatching content changes
* @param root current root node state
*/
public ChangeDispatcher(@Nonnull NodeState root) {
this.root = checkNotNull(root);
}
/**
* Register a new {@link Observer} for receiving notifications about changes reported to
* this change dispatcher. Changes are reported synchronously and clients need to ensure
* to no block any length of time (e.g. by relaying through a {@link BackgroundObserver}).
* <p>
* Clients need to call {@link java.io.Closeable#close()} close} on the returned
* {@code Closeable} instance to stop receiving notifications.
*
* @return a {@link Closeable} instance
*/
@Override
@Nonnull
public Closeable addObserver(final Observer observer) {
observer.contentChanged(root, null);
observers.addObserver(observer);
return new Closeable() {
@Override
public void close() {
observers.removeObserver(observer);
}
};
}
@Override
public synchronized void contentChanged(@Nonnull NodeState root, @Nullable CommitInfo info) {
checkNotNull(root);
observers.contentChanged(root, info);
this.root = root;
}
}