org.fusesource.meshkeeper.distribution.registry.zk.ZooKeeperChildWatcher.java Source code

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Here is the source code for org.fusesource.meshkeeper.distribution.registry.zk.ZooKeeperChildWatcher.java

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/**
 *  Copyright (C) 2009 Progress Software, Inc. All rights reserved.
 *  http://fusesource.com
 *
 *  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.fusesource.meshkeeper.distribution.registry.zk;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.concurrent.atomic.AtomicBoolean;

import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.AsyncCallback.ChildrenCallback;
import org.fusesource.meshkeeper.RegistryWatcher;

/**
 * ZooKeeperWatcher
 * <p>
 * Description:
 * </p>
 * 
 * @author cmacnaug
 * @version 1.0
 */
class ZooKeeperChildWatcher {

    protected final ZooKeeper zk;
    protected final String path;
    private final Watcher watcher;
    private final AtomicBoolean started = new AtomicBoolean(false);
    private final ChildrenCallback callback;
    private final HashSet<RegistryWatcher> watchers = new HashSet<RegistryWatcher>(1);

    public ZooKeeperChildWatcher(ZooKeeper zk, String path) {
        this.zk = zk;
        this.path = path;
        this.watcher = new Watcher() {

            public void process(WatchedEvent event) {
                switch (event.getType()) {
                case NodeChildrenChanged: {
                    //System.out.println("NodeChildrenChangedEvent");
                    watch();
                    break;
                }
                default: {
                    System.out.println("WARNING Got:" + event);
                }
                }
            }
        };

        this.callback = new ChildrenCallback() {

            public void processResult(int rc, String path, Object ctx, List<String> children) {
                handleChildUpdate(path, children);
            }
        };

    }

    private void handleChildUpdate(String path, List<String> children) {
        if (!started.get()) {
            return;
        }
        if (children == null) {
            children = new ArrayList<String>();
        }

        for (RegistryWatcher watcher : watchers) {
            watcher.onChildrenChanged(path, children);
        }
    }

    public void addWatcher(RegistryWatcher watcher) {
        if (watchers.add(watcher)) {
            start();
        }
    }

    /**
     * @param watcher
     *            Removes a watcher from the node.
     * @return true if there are no more watchers.
     */
    public boolean removeWatcher(RegistryWatcher watcher) {
        watchers.remove(watcher);
        if (watchers.isEmpty()) {
            stop();
            return true;
        }
        return false;
    }

    private void start() {
        if (started.compareAndSet(false, true)) {
            watch();
        }
    }

    private void stop() {
        started.set(false);
    }

    private void watch() {
        if (started.get()) {
            //System.out.println("Registering watch for: " + path);
            zk.getChildren(path, watcher, callback, callback);
            //            try {
            //                handleChildUpdate(path, zk.getChildren(path, watcher));
            //            } catch (KeeperException e) {
            //                // TODO Auto-generated catch block
            //                e.printStackTrace();
            //            } catch (InterruptedException e) {
            //                // TODO Auto-generated catch block
            //                e.printStackTrace();
            //            }
        }
    }
}