/*
* 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.plugins.observation;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkState;
import java.io.Closeable;
import java.io.IOException;
import java.util.concurrent.atomic.AtomicReference;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.jcr.observation.EventListener;
import com.google.common.base.Objects;
import org.apache.jackrabbit.api.jmx.EventListenerMBean;
import org.apache.jackrabbit.commons.iterator.EventIteratorAdapter;
import org.apache.jackrabbit.commons.observation.ListenerTracker;
import org.apache.jackrabbit.oak.api.ContentSession;
import org.apache.jackrabbit.oak.core.ImmutableRoot;
import org.apache.jackrabbit.oak.core.ImmutableTree;
import org.apache.jackrabbit.oak.namepath.NamePathMapper;
import org.apache.jackrabbit.oak.spi.commit.CommitInfo;
import org.apache.jackrabbit.oak.spi.commit.Observable;
import org.apache.jackrabbit.oak.spi.commit.Observer;
import org.apache.jackrabbit.oak.spi.state.NodeState;
import org.apache.jackrabbit.oak.spi.whiteboard.Registration;
import org.apache.jackrabbit.oak.spi.whiteboard.Whiteboard;
import org.apache.jackrabbit.oak.spi.whiteboard.WhiteboardUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* A {@code ChangeProcessor} generates observation {@link javax.jcr.observation.Event}s
* based on a {@link EventFilter} and delivers them to an {@link EventListener}.
* <p>
* After instantiation a {@code ChangeProcessor} must be started in order to start
* delivering observation events and stopped to stop doing so.
*/
public class ChangeProcessor implements Observer {
private static final Logger log = LoggerFactory.getLogger(ChangeProcessor.class);
private final ContentSession contentSession;
private final NamePathMapper namePathMapper;
private final ListenerTracker tracker;
private final EventListener listener;
private final AtomicReference<EventFilter> filterRef;
private Closeable observer;
private Registration mbean;
private NodeState previousRoot;
public ChangeProcessor(
ContentSession contentSession, NamePathMapper namePathMapper,
ListenerTracker tracker, EventFilter filter) {
checkArgument(contentSession instanceof Observable);
this.contentSession = contentSession;
this.namePathMapper = namePathMapper;
this.tracker = tracker;
listener = tracker.getTrackedListener();
filterRef = new AtomicReference<EventFilter>(filter);
}
/**
* Set the filter for the events this change processor will generate.
* @param filter
*/
public void setFilter(EventFilter filter) {
filterRef.set(filter);
}
/**
* Start this change processor
* @param whiteboard the whiteboard instance to used for scheduling individual
* runs of this change processor.
* @throws IllegalStateException if started already
*/
public synchronized void start(Whiteboard whiteboard) {
checkState(observer == null, "Change processor started already");
observer = ((Observable) contentSession).addObserver(this);
mbean = WhiteboardUtils.registerMBean(whiteboard, EventListenerMBean.class,
tracker.getListenerMBean(), "EventListener", tracker.toString());
}
/**
* Stop this change processor if running. After returning from this methods no further
* events will be delivered.
* @throws IllegalStateException if not yet started or stopped already
*/
public synchronized void stop() {
checkState(observer != null, "Change processor not started");
try {
mbean.unregister();
observer.close();
} catch (IOException e) {
log.error("Error while stopping change listener", e);
}
}
@Override
public void contentChanged(@Nonnull NodeState root, @Nullable CommitInfo info) {
if (previousRoot != null) {
try {
EventFilter filter = filterRef.get();
if (filter.includeSessionLocal(isLocal(info))
&& filter.includeClusterExternal(isExternal(info))) {
String path = namePathMapper.getOakPath(filter.getPath());
ImmutableTree beforeTree = getTree(previousRoot, path);
ImmutableTree afterTree = getTree(root, path);
EventGenerator events = new EventGenerator(
info, beforeTree, afterTree, filter, namePathMapper);
if (events.hasNext()) {
listener.onEvent(new EventIteratorAdapter(events));
}
}
} catch (Exception e) {
log.warn("Error while dispatching observation events", e);
}
}
previousRoot = root;
}
private boolean isLocal(CommitInfo info) {
// FIXME don't rely on toString for session id
return info != null && Objects.equal(info.getSessionId(), contentSession.toString());
}
private static boolean isExternal(CommitInfo info) {
return info == null;
}
private static ImmutableTree getTree(NodeState nodeState, String path) {
return new ImmutableRoot(nodeState).getTree(path);
}
}