lab.examples.zookeeper.demo.ZooKeeperConnector.java Source code

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Here is the source code for lab.examples.zookeeper.demo.ZooKeeperConnector.java

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/**
 * 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 lab.examples.zookeeper.demo;

import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.Watcher.Event.KeeperState;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.ZooKeeper.States;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;

public class ZooKeeperConnector {

    private String hosts;
    private ZooKeeper zooKeeper;

    // To block any operation until ZooKeeper is connected. It's initialized
    // with count 1, that is, ZooKeeper connect state.
    private java.util.concurrent.CountDownLatch connectedSignal = new java.util.concurrent.CountDownLatch(1);

    /* (non-Javadoc)
     * @see org.springframework.beans.factory.DisposableBean#destroy()
     */
    public void destroy() throws Exception {
        zooKeeper.close();
    }

    /* (non-Javadoc)
     * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet()
     */
    public void init() throws Exception {
        if (hosts == null) {
            throw new IllegalArgumentException(
                    "No hosts set for the ZookeeperConnector. Zookeeper connection cannot be created.");
        }

        zooKeeper = new ZooKeeper(hosts, // ZooKeeper service hosts
                15000, // Session timeout in milliseconds                
                new Watcher() { // Anonymous Watcher Object
                    @Override
                    public void process(WatchedEvent event) {
                        // release lock if ZooKeeper is connected.
                        if (event.getState() == KeeperState.SyncConnected) {
                            connectedSignal.countDown();
                        }
                    }
                });
        connectedSignal.await();
    }

    /**
     * @return the zooKeeper connection
     */
    public ZooKeeper getZooKeeper() {
        // Verify ZooKeeper's validity
        if (zooKeeper == null || !zooKeeper.getState().equals(States.CONNECTED)) {
            throw new IllegalStateException("ZooKeeper is not connected.");
        }
        return zooKeeper;
    }

    public String getHosts() {
        return hosts;
    }

    public void setHosts(String hosts) {
        this.hosts = hosts;
    }

}