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/**
* Copyright 2010 the original author or authors.
*
* 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.I0Itec.zkclient;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import org.I0Itec.zkclient.exception.ZkNoNodeException;
import org.apache.log4j.Logger;
/**
* @param
* The data type that is being watched.
*/
public final class ContentWatcher implements IZkDataListener {
private static final Logger LOG = Logger.getLogger(ContentWatcher.class);
private Lock _contentLock = new ReentrantLock(true);
private Condition _contentAvailable = _contentLock.newCondition();
private Holder _content;
private String _fileName;
private ZkClient _zkClient;
public ContentWatcher(ZkClient zkClient, String fileName) {
_fileName = fileName;
_zkClient = zkClient;
}
public void start() {
_zkClient.subscribeDataChanges(_fileName, this);
readData();
LOG.debug("Started ContentWatcher");
}
@SuppressWarnings("unchecked")
private void readData() {
try {
setContent((T) _zkClient.readData(_fileName));
} catch (ZkNoNodeException e) {
// ignore if the node has not yet been created
}
}
public void stop() {
_zkClient.unsubscribeDataChanges(_fileName, this);
}
public void setContent(T data) {
LOG.debug("Received new data: " + data);
_contentLock.lock();
try {
_content = new Holder(data);
_contentAvailable.signalAll();
} finally {
_contentLock.unlock();
}
}
@SuppressWarnings("unchecked")
@Override
public void handleDataChange(String dataPath, Object data) {
setContent((T) data);
}
@Override
public void handleDataDeleted(String dataPath) {
// ignore
}
public T getContent() throws InterruptedException {
_contentLock.lock();
try {
while (_content == null) {
_contentAvailable.await();
}
return _content.get();
} finally {
_contentLock.unlock();
}
}
}