3. ZooKeeper客户端(一)

ZooKeeper常用客户端有三种：原生客户端、zkClient、curator

项目中使用前，需要导入相关依赖

<dependencies>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
    </dependency>
    <dependency>
        <groupId>org.apache.zookeeper</groupId>
        <artifactId>zookeeper</artifactId>
        <version>3.4.12</version>
    </dependency>
    <dependency>
        <groupId>com.101tec</groupId>
        <artifactId>zkclient</artifactId>
        <version>0.10</version>
    </dependency>

    <dependency>
        <groupId>org.apache.curator</groupId>
        <artifactId>curator-framework</artifactId>
        <version>4.0.0</version>
    </dependency>
    <dependency>
        <groupId>org.apache.curator</groupId>
        <artifactId>curator-recipes</artifactId>
        <version>4.0.0</version>
    </dependency>
</dependencies>

原生客户端

创建会话

不使用监听

public class TestCreateSession {
    /*服务地址*/
    private static final String ZK_SERVER = "127.0.0.1:2181";
    @Test
    public void createSession2() throws IOException {
        ZooKeeper zk = new ZooKeeper(ZK_SERVER, 50000, null);
        System.out.println("zk.getState() = " + zk.getState());
    }
}

---

zk.getState() = CONNECTING　

通过之前的学习可以知道，CONNECTING标志客户端正在连接，并不能确保已经连接上zk服务。可能发生还没有连接到zk服务就进行对zk访问的情况

使用监听

public class TestCreateSession {
    /*服务地址*/
    private static final String ZK_SERVER = "127.0.0.1:2181";
    /*倒计时器*/
    private CountDownLatch latch = new CountDownLatch(1);
    @Test
    public void createSession() throws IOException, InterruptedException {
        ZooKeeper zk = new ZooKeeper(ZK_SERVER, 50000, new Watcher() {
            @Override
            public void process(WatchedEvent event) {
                if (event.getState() == Event.KeeperState.SyncConnected){/*确保zk已连接*/
                    latch.countDown();
                }
            }
        });
        latch.await();
        System.out.println("zk.getState() = " + zk.getState());
    }
}

---

zk.getState() = CONNECTED

使用监听机制可以确保在ZooKeeper初始化完成前进行等待，初始化完成再进行后续操作

客户端基本操作

public class TestJavaApi implements Watcher {
    /*zk服务地址*/
    private static final String ZK_SERVER = "127.0.0.1:2181";
    /*会话连接超时时间*/
    private static final int SESSION_TIMEOUT = 50000;
    /*指定目录【节点】*/
    private static final String ZK_PATH = "/zkDir";
    /*客户端连接会话*/
    private ZooKeeper zk = null;

    /*倒计时器*/
    private CountDownLatch latch = new CountDownLatch(1);
    /**
     * 事件被触发时的动作
     * @param event 事件
     */
    @Override
    public void process(WatchedEvent event) {
        System.out.println("收到事件通知：" + zk.getState() +"\n");
        if (event.getState() == Event.KeeperState.SyncConnected){
            latch.countDown();
        }
    }

    /**
     * 创建zk会话连接
     * @param connectString     zk服务器地址列表，可以是"地址1，地址2，...."
     * @param sessionTimeout    Session超时时间
     */
    public void createZkSession(String connectString, int sessionTimeout){
        try {
            zk = new ZooKeeper(connectString,sessionTimeout,this);
            latch.await();
            System.out.println("zk.getState() = " + zk.getState());
        } catch (IOException|InterruptedException e) {
            System.out.println("连接创建失败");
            e.printStackTrace();
        }
    }

    /**
     * 关闭zk会话
     */
    public void releaseSession(){
        try {
            zk.close();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    /**
     * 创建节点【目录、文件】
     * @param path  节点
     * @param data  节点数据
     * @return
     */
    public boolean createNode(String path,String data){
        try {
            String node = zk.create(path/*节点path*/,
                    data.getBytes()/*节点数据*/,
                    ZooDefs.Ids.OPEN_ACL_UNSAFE/*权限控制  OPEN_ACL_UNSAFE相当于world:anyone*/,
                    CreateMode.EPHEMERAL)/*临时节点*/;
            System.out.println("节点创建成功，node = " + node);
            return true;
        } catch (KeeperException|InterruptedException e) {
            System.out.println("节点创建失败");
            e.printStackTrace();
        }
        return false;
    }

    /**
     * 获取节点数据
     * @param path  节点路径
     * @return
     */
    public String readNode(String path){
        try {
            byte[] data = zk.getData(path, true, null);
            String nodeData = new String(data,"utf-8");
            //System.out.println("获取"+path+"节点数据:"+nodeData);
            return nodeData;
        } catch (KeeperException | InterruptedException | UnsupportedEncodingException e) {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * 修改节点数据
     * @param path      节点path
     * @param newData   节点新数据
     * @return
     */
    public boolean writeNode(String path,String newData){
        try {
            Stat stat = zk.setData(path, newData.getBytes(), -1);
            System.out.println("节点["+path+"]修改成功");
            return true;
        } catch (KeeperException|InterruptedException e) {
            e.printStackTrace();
        }
        return false;
    }

    /**
     * 删除指定节点
     * @param path  节点path
     */
    public void deleteNode(String path){
        try {
            zk.delete(path,-1);
            System.out.println("节点["+path+"]删除成功");
        } catch (InterruptedException|KeeperException e) {
            System.out.println("节点["+path+"]删除失败");
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        TestJavaApi api = new TestJavaApi();
        api.createZkSession(ZK_SERVER,SESSION_TIMEOUT);
        if(api.createNode(ZK_PATH,"初始节点内容")){
            System.out.println("第一次读"+ZK_PATH+"节点数据："+api.readNode(ZK_PATH));
            api.writeNode(ZK_PATH,"修改ZK_PATH节点数据");
            System.out.println("第二次读"+ZK_PATH+"节点数据："+api.readNode(ZK_PATH));
            api.deleteNode(ZK_PATH);
        }
        api.releaseSession();
    }
}
/**
************输出结果***********
    收到事件通知：CONNECTED

    zk.getState() = CONNECTED
    节点创建成功，node = /zkDir
    第一次读/zkDir节点数据：初始节点内容
    收到事件通知：CONNECTED

    节点[/zkDir]修改成功
    第二次读/zkDir节点数据：修改ZK_PATH节点数据
    收到事件通知：CONNECTED

    节点[/zkDir]删除成功
*/

 

watch机制

public class ZkWatcher implements Watcher {
    private static final String ZK_SERVER = "127.0.0.1:2181";
    private static final int SESSION_TIMEOUT = 15000;
    private static final String PARENT_PATH ="/testWatcher";
    private static final String CHILDREN_PATH = "/testWatcher/children";
    private ZooKeeper zk = null;
    /*定义原子变量，用于计算进入监听的次数*/
    private static AtomicInteger seq = new AtomicInteger();
    /*会话进入标志*/
    private static final String LOG_PREFIX_OF_MAIN = "【main】";

    /*倒计时器*/
    private CountDownLatch latch = new CountDownLatch(1);
    @Override
    public void process(WatchedEvent event) {
        System.out.println("**************进入process方法**************");
        System.out.println("event = " + event);
        /*模拟业务连接初始化工作*/
        TimeUtils.threadSleep(200);
        if (event == null) { return; }
        /*连接状态*/
        Event.KeeperState eventState = event.getState();
        /*事件类型*/
        Event.EventType eventType = event.getType();
        /*受影响的路径*/
        String eventPath = event.getPath();
        /*进入监听标志*/
        String logPreFix = "【watcher-"+seq.incrementAndGet()+"】";
        System.out.println(logPreFix + "收到watcher通知");
        System.out.println(logPreFix + "连接状态：\t"+eventState.toString());
        System.out.println(logPreFix + "事件类型：\t"+eventType.toString());

        if(Event.KeeperState.SyncConnected == eventState){
            if (Event.EventType.None == eventType){/*成功连接上ZK服务器*/
                System.out.println(logPreFix + "成功连接上ZK服务器");
                latch.countDown();
            }else if (Event.EventType.NodeCreated == eventType){/*创建节点*/
                System.out.println(logPreFix + "创建节点");
                TimeUtils.threadSleep(100);
                /*使用监听*/
                exist(eventPath,true);
            }else if (Event.EventType.NodeChildrenChanged == eventType){
                System.out.println(logPreFix + "子节点变更");
                TimeUtils.threadSleep(1000);
                System.out.println(logPreFix + "子节点列表：" + getChildren(eventPath,true));
            }else if (Event.EventType.NodeDataChanged == eventType){
                System.out.println(logPreFix + "修改节点数据");
                TimeUtils.threadSleep(100);
                System.out.println(logPreFix + "修改后节点内容：" + readNode(eventPath, true));
            }else if (Event.EventType.NodeDeleted == eventType){
                System.out.println(logPreFix + "删除节点");
                System.out.println(logPreFix + "节点 " + eventPath + " 被删除");
            }
        }else if(Event.KeeperState.Disconnected == eventState){
            System.out.println(logPreFix + "与zk服务器断开连接");
        }else if(Event.KeeperState.AuthFailed == eventState){
            System.out.println(logPreFix + "验证失败");
        }else if(Event.KeeperState.Expired == eventState){
            System.out.println(logPreFix + "会话超时");
        }
        System.out.println("----------------------------------------");
    }
    /**
     * 创建ZK连接
     * @param connectAddr ZK服务器地址列表
     * @param sessionTimeout Session超时时间
     */
    public void createConnection(String connectAddr, int sessionTimeout) {
        this.releaseConnection();
        try {
            zk = new ZooKeeper(connectAddr, sessionTimeout, this);
            System.out.println(LOG_PREFIX_OF_MAIN + "开始连接zk服务器");
            latch.await();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 关闭ZK连接
     */
    public void releaseConnection() {
        if (this.zk != null) {
            try {
                this.zk.close();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * 创建节点
     * @param path 节点路径
     * @param data 数据内容
     * @return
     */
    public boolean createPath(String path, String data) {
        try {/*设置监控(由于zookeeper的监控都是一次性的所以 每次必须设置监控)*/
            zk.exists(path, true);
            System.out.println(LOG_PREFIX_OF_MAIN + "节点创建成功, Path: " +
                    this.zk.create(    /*路径*/
                            path,/*数据*/
                            data.getBytes(),/*所有可见*/
                            ZooDefs.Ids.OPEN_ACL_UNSAFE,/*永久存储*/
                            CreateMode.PERSISTENT ) +
                    ", content: " + data);
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        }
        return true;
    }

    /**
     * 删除所有节点
     */
    public void deleteAllTestPath() {
        if(this.exist(CHILDREN_PATH, false) != null){
            this.deleteNode(CHILDREN_PATH);
        }
        if(this.exist(PARENT_PATH, false) != null){
            this.deleteNode(PARENT_PATH);
        }
    }

    /**
     * 删除指定节点
     * @param path
     */
    public void deleteNode(String path) {
        try {
            zk.delete(path,-1);
            System.out.println(LOG_PREFIX_OF_MAIN + "删除节点成功，path：" + path);
        } catch (InterruptedException|KeeperException e) {
            e.printStackTrace();
        }
    }

    /**
     * 获取节点内容
     * @param path
     * @param needWatch
     * @return
     */
    public String readNode(String path, boolean needWatch) {
        try {
            byte[] data = zk.getData(path, needWatch, null);
            return new String(data,"utf-8");
        } catch (KeeperException|InterruptedException|UnsupportedEncodingException e) {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * 获取指定节点的子节点列表
     * @param path
     * @param needWatch
     * @return
     */
    public List<String> getChildren(String path, boolean needWatch) {
        try {
            return this.zk.getChildren(path, needWatch);
        } catch (KeeperException|InterruptedException e) {
            e.printStackTrace();
            return null;
        }
    }
    /**
     * 更新指定节点数据内容
     * @param path 节点路径
     * @param data 数据内容
     * @return
     */
    public boolean writeNode(String path, String data) {
        try {
            System.out.println(LOG_PREFIX_OF_MAIN + "更新数据成功，path：" + path + ", stat: " +
                    this.zk.setData(path, data.getBytes(), -1));
        } catch (Exception e) {
            e.printStackTrace();
        }
        return false;
    }
    /**
     * path节点是否存在
     * @param path
     * @param needWatch
     * @return
     */
    public Stat exist(String path, boolean needWatch) {
        try {
            return zk.exists(path,needWatch);
        } catch (KeeperException|InterruptedException e) {
            e.printStackTrace();
            return null;
        }
    }

    public static void main(String[] args) throws Exception {
        //建立watcher
        ZkWatcher watcher = new ZkWatcher();
        //创建连接
        watcher.createConnection(ZK_SERVER, SESSION_TIMEOUT);
        //System.out.println(zkWatch.zk.toString());
        Thread.sleep(1000);
        // 清理节点
        watcher.deleteAllTestPath();
        if (watcher.createPath(PARENT_PATH, System.currentTimeMillis() + "")) {
            System.out.println("---------------------- read parent ----------------------------");
            /*
            读取数据，在操作节点数据之前先调用zookeeper的getData()方法是为了可以watch到对节点的操作。
            watch是一次性的，也就是说，如果第二次又重新调用了setData()方法，在此之前需要重新调用一次。
            */
            watcher.readNode(PARENT_PATH, true);
            watcher.writeNode(PARENT_PATH, System.currentTimeMillis() + "");
            System.out.println("---------------------- read children path ----------------------------");
            /*
            读取子节点，设置对子节点变化的watch，如果不写该方法，则在创建子节点是只会输出NodeCreated，
            而不会输出NodeChildrenChanged，也就是说创建子节点时没有watch。
            如果是递归的创建子节点，如path="/p/c1/c2"的话，getChildren(PARENT_PATH, ture)只会在
            创建c1时watch，输出c1的NodeChildrenChanged，而不会输出创建c2时的NodeChildrenChanged，
            如果watch到c2的NodeChildrenChanged，则需要再调用一次getChildren(String path, true)方法，
            其中path="/p/c1"
             */
            watcher.getChildren(PARENT_PATH, true);
            Thread.sleep(1000);
            // 创建子节点，同理如果想要watch到NodeChildrenChanged状态，需要调用getChildren(CHILDREN_PATH, true)
            watcher.createPath(CHILDREN_PATH, System.currentTimeMillis() + "");
            Thread.sleep(1000);
            watcher.readNode(CHILDREN_PATH, true);
            watcher.writeNode(CHILDREN_PATH, System.currentTimeMillis() + "");
        }
        Thread.sleep(20000);
        // 清理节点
        watcher.deleteAllTestPath();
        Thread.sleep(1000);
        watcher.releaseConnection();
    }
}

class TimeUtils{
    public static void threadSleep(long mills){
        try {
            Thread.sleep(mills);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

/*
*********输出结果********
【main】开始连接zk服务器
**************进入process方法**************
event = WatchedEvent state:SyncConnected type:None path:null
【watcher-1】收到watcher通知
【watcher-1】连接状态：    SyncConnected
【watcher-1】事件类型：    None
【watcher-1】成功连接上ZK服务器
----------------------------------------
**************进入process方法**************
event = WatchedEvent state:SyncConnected type:NodeCreated path:/testWatcher
【main】节点创建成功, Path: /testWatcher, content: 1567510219582
---------------------- read parent ----------------------------
【main】更新数据成功，path：/testWatcher, stat: 223,224,1567510219588,1567510219598,1,0,0,0,13,0,223

---------------------- read children path ----------------------------
【watcher-2】收到watcher通知
【watcher-2】连接状态：    SyncConnected
【watcher-2】事件类型：    NodeCreated
【watcher-2】创建节点
----------------------------------------
**************进入process方法**************
event = WatchedEvent state:SyncConnected type:NodeDataChanged path:/testWatcher
【watcher-3】收到watcher通知
【watcher-3】连接状态：    SyncConnected
【watcher-3】事件类型：    NodeDataChanged
【watcher-3】修改节点数据
【watcher-3】修改后节点内容：1567510219598
----------------------------------------
**************进入process方法**************
event = WatchedEvent state:SyncConnected type:NodeCreated path:/testWatcher/children
【main】节点创建成功, Path: /testWatcher/children, content: 1567510220605
【watcher-4】收到watcher通知
【watcher-4】连接状态：    SyncConnected
【watcher-4】事件类型：    NodeCreated
【watcher-4】创建节点
----------------------------------------
**************进入process方法**************
event = WatchedEvent state:SyncConnected type:NodeChildrenChanged path:/testWatcher
【watcher-5】收到watcher通知
【watcher-5】连接状态：    SyncConnected
【watcher-5】事件类型：    NodeChildrenChanged
【watcher-5】子节点变更
【main】更新数据成功，path：/testWatcher/children, stat: 225,226,1567510220606,1567510221615,1,0,0,0,13,0,225

【watcher-5】子节点列表：[children]
----------------------------------------
**************进入process方法**************
event = WatchedEvent state:SyncConnected type:NodeDataChanged path:/testWatcher/children
【watcher-6】收到watcher通知
【watcher-6】连接状态：    SyncConnected
【watcher-6】事件类型：    NodeDataChanged
【watcher-6】修改节点数据
【watcher-6】修改后节点内容：1567510221615
----------------------------------------
**************进入process方法**************
event = WatchedEvent state:SyncConnected type:NodeDeleted path:/testWatcher/children
【main】删除节点成功，path：/testWatcher/children
【main】删除节点成功，path：/testWatcher
【watcher-7】收到watcher通知
【watcher-7】连接状态：    SyncConnected
【watcher-7】事件类型：    NodeDeleted
【watcher-7】删除节点
【watcher-7】节点 /testWatcher/children 被删除
----------------------------------------
**************进入process方法**************
event = WatchedEvent state:SyncConnected type:NodeChildrenChanged path:/testWatcher
【watcher-8】收到watcher通知
【watcher-8】连接状态：    SyncConnected
【watcher-8】事件类型：    NodeChildrenChanged
【watcher-8】子节点变更

*/

ZooKeeper认证机制