zookeeper -- 第八章 zk开源客户端 Curator介绍 （下）

一、读取数据

构建操做包装类（Builder）: GetDataBuilder getData() ---- CuratorFramework

GetDataBuilder

• storingStatIn(org.apache.zookeeper.data.Stat stat) // 把服务器端获取的状态数据存储到stat对象

• Byte[] forPath (String path) // 节点路劲

public void readNode(String path) throws Exception {
		Stat stat = new Stat();
		byte[] data = client.getData().storingStatIn(stat).forPath(path);
		System.out.println("读取节点" + path + "的数据:" + new String(data));
		System.out.println(stat.toString());
	}

二、更新数据

构建操做包装类 （Builder） SetDataBuilder setData() ---- CuratorFramework

SetDataBuilder

• withVersion (int version) // 特定版本号

• forPath (String path, byte[] data) // 节点路劲

• forPath (String path) // 节点路劲

public void updateNode(String path, byte[] data, int version)
			throws Exception {
		client.setData().withVersion(version).forPath(path, data);
	}

三、读取子节点

构建操做包装类（Builder）:GetChildrenBuilder getChildren() --- CuratorFramework

GetChildrenBuilder

• storingStatIn(org.apache.zookeeper.data.Stat stat) // 把服务器端获取的状态数据存储到stat对象

• Byte[] forPath(String path) // 节点路径

• usingWatcher(org.apache.zookeeper.Watcher watcher) // 设置watcher ,相似zk自己api ,也只能使用一次

• usingWatcher(CuratorWatcher watcher) // 设置watcher ,相似于zk自己的api,也只能使用一次

public void getChildren(String path) throws Exception {
		List<String> children = client.getChildren().usingWatcher(new WatcherTest()).forPath("/curator");
		for (String pth : children) {
			System.out.println("child=" + pth);
		}
	}

四、设置watcher

一、 NodeCache

• 监听数据节点的内容变动

• 监听节点的建立，即若是指定的节点不存在，则节点建立后，会触发这个监听

二、PathChildrenCache

• 监听指定节点的子节点变化状况

• 包括：新增子节点 子节点数据变动和子节点删除

三、 NodeCache介绍

构造函数

• NodeCache(CuratorFramework client, String path)

• NodeCache(CuratorFramework client, String path, boolean dataIsCompressed)

client : 客户端实例

path : 数据节点路径

dataIsCompressed : 是否进行数据压缩

• 回调接口

public interface NodeCacheListener {
    // 没有参数，怎么获取事件信息以及节点数据
    void nodeChanged() throws Exception;
}

四、PathChildrenCache介绍

一、 构造函数

public PathChildrenCache(CuratorFramework client, String path, boolean cacheData) {
        this(client, path, cacheData, false, new CloseableExecutorService(Executors.newSingleThreadExecutor(defaultThreadFactory), true));
    }

    public PathChildrenCache(CuratorFramework client, String path, boolean cacheData, ThreadFactory threadFactory) {
        this(client, path, cacheData, false, new CloseableExecutorService(Executors.newSingleThreadExecutor(threadFactory), true));
    }

    public PathChildrenCache(CuratorFramework client, String path, boolean cacheData, boolean dataIsCompressed, ThreadFactory threadFactory) {
        this(client, path, cacheData, dataIsCompressed, new CloseableExecutorService(Executors.newSingleThreadExecutor(threadFactory), true));
    }

    public PathChildrenCache(CuratorFramework client, String path, boolean cacheData, boolean dataIsCompressed, ExecutorService executorService) {
        this(client, path, cacheData, dataIsCompressed, new CloseableExecutorService(executorService));
    }

二、 回调接口

public interface PathChildrenCacheListener {
    void childEvent(CuratorFramework var1, PathChildrenCacheEvent var2) throws Exception;
}

三、 构造函数参数

client : 客户端实例

path : 数据节点路径

dataIsCompressed ： 是否进行数据压缩

cacheData ： 用于配置是否把节点内容缓存起来，若是配置true,那么客户端在接收到节点列表变动时，也

可以获取到节点的数据内容，若是为false则没法取到数据内容

threadFactory : 经过这两个参数构造专门的线程池来处理事件通知

ExecutorService

四、 监听接口

public static enum Type {
        CHILD_ADDED,                                // 新增子节点（CHILD_ADDED）
        CHILD_UPDATED,                           // 子节点数据变动（CHILD_UPDATED）
        CHILD_REMOVED,                          // 子节点删除（CHILD_REMOVED）
        CONNECTION_SUSPENDED,
        CONNECTION_RECONNECTED,
        CONNECTION_LOST,
        INITIALIZED;

        private Type() {
        }
    }

五、 PathChildrenCache.StartMode

public static enum StartMode {
         // 异步初始化cache
        NORMAL,  
                          
        // 同步初始化客户端的cache,及建立cache后，就从服务器端拉入对应的数据
        BUILD_INITIAL_CACHE,     

        // 异步初始化，初始化完成触发事件， PathChildrenCacheEvent.Type.INITIALIZED
        POST_INITIALIZED_EVENT;

        private StartMode() {
        }
    }

六、 代码演示

public void addChildWatcher(String path) throws Exception {
		final PathChildrenCache cache = new PathChildrenCache(this.client,
				path, true);
		cache.start(StartMode.POST_INITIALIZED_EVENT);
		System.out.println(cache.getCurrentData().size());
		//byte childone[] = cache.getCurrentData().get(0).getData();
//		System.out.println("childone:"
//				+ cache.getCurrentData().get(0).getPath() + ";data="
//				+ new String(childone));
		cache.getListenable().addListener(new PathChildrenCacheListener() {
			public void childEvent(CuratorFramework client,
					PathChildrenCacheEvent event) throws Exception {
				if(event.getType().equals(PathChildrenCacheEvent.Type.INITIALIZED)){
					System.out.println("客户端子节点cache初始化数据完成");
					System.out.println("size="+cache.getCurrentData().size());
				}else if(event.getType().equals(PathChildrenCacheEvent.Type.CHILD_ADDED)){
					System.out.println("添加子节点:"+event.getData().getPath());
					System.out.println("修改子节点数据:"+new String(event.getData().getData()));
				}else if(event.getType().equals(PathChildrenCacheEvent.Type.CHILD_REMOVED)){
					System.out.println("删除子节点:"+event.getData().getPath());
				}else if(event.getType().equals(PathChildrenCacheEvent.Type.CHILD_UPDATED)){
					System.out.println("修改子节点数据:"+event.getData().getPath());
					System.out.println("修改子节点数据:"+new String(event.getData().getData()));
				}
			}
		});
	}