上文大概讲解了利用zookeeper如何实现注册中心的。本文主要是从源码角度说明下。代码都在模块motan-registry-zookeeper中，其实在在这个模块中就3个类。
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ZkNodeType: 跟上文的图中的节点类型是对应的
enum ZkNodeType {AVAILABLE_SERVER,UNAVAILABLE_SERVER,CLIENT }
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ZookeeperRegistryFactory：顾名思义
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zookeeper注册中心的注册工厂ZookeeperRegistry
最重要的就是创建节点
@Overrideprotected void doRegister(URL url) {try {// 防止旧节点未正常注销 removeNode(url, ZkNodeType.AVAILABLE_SERVER);removeNode(url, ZkNodeType.UNAVAILABLE_SERVER);createNode(url, ZkNodeType.UNAVAILABLE_SERVER);} catch (Throwable e) {throw new MotanFrameworkException(String.format("Failed to register %s to zookeeper(%s), cause: %s", url, getUrl(), e.getMessage()));}}
还有client对server列表的监听：注释很多，自己看。
@Overrideprotected void doSubscribe(final URL url, final NotifyListener notifyListener) {try {ConcurrentHashMap<NotifyListener, IZkChildListener> childChangeListeners = urlListeners.get(url);if (childChangeListeners == null) {urlListeners.putIfAbsent(url, new ConcurrentHashMap<NotifyListener, IZkChildListener>());childChangeListeners = urlListeners.get(url);}IZkChildListener zkChildListener = childChangeListeners.get(notifyListener);if (zkChildListener == null) {childChangeListeners.putIfAbsent(notifyListener, new IZkChildListener() {@Overridepublic void handleChildChange(String parentPath, List<String> currentChilds) {ZookeeperRegistry.this.notify(url, notifyListener, nodeChildsToUrls(parentPath, currentChilds));LoggerUtil.info(String.format("[ZookeeperRegistry] service list change: path=%s, currentChilds=%s", parentPath, currentChilds.toString()));}});zkChildListener = childChangeListeners.get(notifyListener);}// 防止旧节点未正常注销 removeNode(url, ZkNodeType.CLIENT);createNode(url, ZkNodeType.CLIENT);// 订阅server节点，并获取当前可用serverString serverTypePath = toNodeTypePath(url, ZkNodeType.AVAILABLE_SERVER);List<String> currentChilds = zkClient.subscribeChildChanges(serverTypePath, zkChildListener);LoggerUtil.info(String.format("[ZookeeperRegistry] subscribe: path=%s, info=%s", toNodePath(url, ZkNodeType.AVAILABLE_SERVER), url.toFullStr()));notify(url, notifyListener, nodeChildsToUrls(serverTypePath, currentChilds));} catch (Throwable e) {throw new MotanFrameworkException(String.format("Failed to subscribe %s to zookeeper(%s), cause: %s", url, getUrl(), e.getMessage()));}}
http://www.cnblogs.com/scott19820130/p/4940066.html