com.anteam.demo.zookeeper.DataMonitor.java Source code

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Here is the source code for com.anteam.demo.zookeeper.DataMonitor.java

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/*
 *  Copyright 2010 shanyong.wang
 *
 *  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 com.anteam.demo.zookeeper;

import org.apache.zookeeper.AsyncCallback.StatCallback;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.KeeperException.Code;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;

import java.util.Arrays;

/**
 * @author <a href="mailto:wsysisibeibei@gmail.com">sisibeibei</a>
 * @ClassName: DataMonitor
 * @Package com.anteam.demo.zookeeper
 * @Description: monitors the data in the ZooKeeper tree
 * @date 2013-4-22 ?2:13:13
 */

public class DataMonitor implements Watcher, StatCallback {

    ZooKeeper zk;

    String znode;

    Watcher chainedWatcher;

    boolean dead;

    DataMonitorListener listener;

    byte prevData[];

    public DataMonitor(ZooKeeper zk, String znode, Watcher chainedWatcher, DataMonitorListener listener) {
        this.zk = zk;
        this.znode = znode;
        this.chainedWatcher = chainedWatcher;
        this.listener = listener;
        // Get things started by checking if the node exists. We are going
        // to be completely event driven
        zk.exists(znode, true, this, null);
    }

    /**
     * Other classes use the DataMonitor by implementing this method
     */
    public interface DataMonitorListener {
        /**
         * The existence status of the node has changed.
         */
        void exists(byte data[]);

        /**
         * The ZooKeeper session is no longer valid.
         *
         * @param rc the ZooKeeper reason code
         */
        void closing(int rc);
    }

    @SuppressWarnings("deprecation")
    public void process(WatchedEvent event) {
        System.out.println("----------------------------------------");
        System.out.println("event:" + event);
        String path = event.getPath();
        System.out.println("DataMonitor.process.path:" + path);
        if (event.getType() == Event.EventType.None) {
            // We are are being told that the state of the
            // connection has changed
            switch (event.getState()) {
            case SyncConnected:
                // In this particular example we don't need to do anything
                // here - watches are automatically re-registered with
                // server and any watches triggered while the client was
                // disconnected will be delivered (in order of course)
                break;
            case Expired:
                // It's all over
                dead = true;
                listener.closing(KeeperException.Code.SessionExpired);
                break;
            default:
                break;
            }
        } else {
            if (path != null && path.equals(znode)) {
                // Something has changed on the node, let's find out
                zk.exists(znode, true, this, null);
            }
        }
        if (chainedWatcher != null) {
            chainedWatcher.process(event);
        }
    }

    @SuppressWarnings("deprecation")
    public void processResult(int rc, String path, Object ctx, Stat stat) {
        boolean exists;
        System.out.println("DataMonitor.processResult.rc:" + rc);
        switch (rc) {
        case Code.Ok:
            exists = true;
            break;
        case Code.NoNode:
            exists = false;
            break;
        case Code.SessionExpired:
        case Code.NoAuth:
            dead = true;
            listener.closing(rc);
            return;
        default:
            // Retry errors
            zk.exists(znode, true, this, null);
            return;
        }

        byte b[] = null;
        System.out.println("DataMonitor.processResult.exists:" + exists);
        if (exists) {
            try {
                b = zk.getData(znode, false, null);
            } catch (KeeperException e) {
                // We don't need to worry about recovering now. The watch
                // callbacks will kick off any exception handling
                e.printStackTrace();
                System.out.println("error");
            } catch (InterruptedException e) {
                System.out.println("error");
                e.printStackTrace();
            }
        }
        if (b != null)
            System.out.println("DataMonitor.processResult.b:" + new String(b));
        if (prevData != null)
            System.out.println("DataMonitor.processResult.prevData:" + new String(prevData));

        if ((b == null && b != prevData) || (b != null && !Arrays.equals(prevData, b))) {

            listener.exists(b);
            prevData = b;
        }
    }
}