zoukankan      html  css  js  c++  java

  • Java客户端API

    添加依赖

    <dependency>
      <groupId>org.apache.zookeeper</groupId>
      <artifactId>zookeeper</artifactId>
      <version>3.4.10</version>
    </dependency>

    创建会话

    • 构造器方法
    ZooKeeper(String connectString, int sessionTimeout, Watcher watcher)
ZooKeeper(String connectString, int sessionTimeout, Watcher watcher, boolean canBeReadOnly)
ZooKeeper(String connectString, int sessionTimeout, Watcher watcher, long sessionId, byte[] sessionPasswd)
ZooKeeper(String connectString, int sessionTimeout, Watcher watcher, long sessionId, byte[] sessionPasswd, boolean canBeReadOnly)
    • 参数详解
    参数名 描述
    connectString 形如ip:port,ip:port/path1/path2，表示zk服务器列表，带path路径的表示基于此path操作
    sessionTimeout 客户端会话超时时间，毫秒值，在sessionTimeout时间内没有进行有效的心跳检测，则认为会话超时
    watcher 默认监听器，可以不设置，传null即可
    canBeReadOnly boolean值，true表示只读，默认为false
    sessionId和sessionPasswd 会话id和会话的秘钥，当一个会话创建后，会自动生成对应的id和秘钥，主要用来恢复会话
    • 例子
    package com.banary.base;

import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;

import java.util.concurrent.CountDownLatch;

public class ZookeeperFactory {

    private static CountDownLatch countDownLatch = new CountDownLatch(1);

    public static void main(String[] args) throws Exception {
        createZk2();
    }

    public static void createZk1() throws Exception{
        ZooKeeper zooKeeper = new ZooKeeper("localhost:2181", 5000, new DemoWatcher());
        System.out.println(zooKeeper.getState());
        countDownLatch.await();
        System.out.println("zk实例创建成功");
    }

    public static void createZk2() throws Exception{
        ZooKeeper zooKeeper = new ZooKeeper("localhost:2181", 5000, new DemoWatcher());
        System.out.println(zooKeeper.getState());
        countDownLatch.await();

        long sessionId = zooKeeper.getSessionId();
        byte[] sessionPasswd = zooKeeper.getSessionPasswd();

        //使用错的sessionId和sessionPasswd
        zooKeeper = new ZooKeeper("localhost:2181", 5000, new DemoWatcher(), 1l, "test".getBytes());
        //使用对的sessionId和sessionPasswd
        zooKeeper = new ZooKeeper("localhost:2181", 5000, new DemoWatcher(), sessionId, sessionPasswd);
        Thread.sleep(Integer.MAX_VALUE);
    }

    private static class DemoWatcher implements Watcher{
        public void process(WatchedEvent watchedEvent) {
            System.out.println("收到zk event:" + watchedEvent);
            countDownLatch.countDown();
        }
    }
}
    • 注意
      创建zk对象的方法是异步的，此处采用CountDownLatch实现同步

    创建节点

    • 方法（不支持递归创建，如果该节点已存在，会抛出异常NodeExistsException）
    #同步方法
public String create(String path, byte[] data, List<ACL> acl, CreateMode createMode) throws KeeperException, InterruptedException
#异步方法
public void create(String path, byte[] data, List<ACL> acl, CreateMode createMode, StringCallback cb, Object ctx)
    • 参数详解
    参数名 描述
    path 要创建的数据节点的路径
    data 字节数组，该节点的初始内容，需要自己序列化成字节数组
    acl 节点的安全策略，详见ZooDefs.Ids
    createMode 枚举类型，相见CreateMode
    cb 异步创建时的回调函数，需要开发者自己实现对应的AsyncCallback子接口，如StringCallback，重写void processResult(int var1, String var2, Object var3, String var4)方法，当zk服务器创建完节点，客户端自动调用该方法
    ctx 回调函数上下文，和回调函数一起使用
    • 例子
    package com.banary.base;

import org.apache.zookeeper.*;

import java.util.concurrent.CountDownLatch;

public class CreateDemo {

    private static CountDownLatch countDownLatch = new CountDownLatch(1);

    public static void main(String[] args) throws Exception{
        asyncCreate();
    }

    /**
     * 同步创建
     * @throws Exception
     */
    public static void syncCreate() throws Exception{
        ZooKeeper zooKeeper = new ZooKeeper("localhost:2181", 5000, new DemoWatcher());
        //阻塞，直到zk链接成功
        countDownLatch.await();
        //创建临时节点，没有权限限制
        String path1 = zooKeeper.create("/zk-test-ephemeral-", "1".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
        System.out.println("临时节点1创建成功："+ path1);
        //创建临时顺序节点，没有权限限制
        String path2 = zooKeeper.create("/zk-test-ephemeral-", "1".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
        System.out.println("临时节点2创建成功：" + path2);
    }

    /**
     * 异步创建
     * @throws Exception
     */
    public static void asyncCreate() throws Exception{
        ZooKeeper zooKeeper = new ZooKeeper("localhost:2181", 5000, new DemoWatcher());
        //阻塞，直到zk链接成功
        countDownLatch.await();
        //创建临时节点，没有权限限制
        zooKeeper.create("/zk-test-ephemeral-", "1".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL,
                new DemoCallback(), "path1");
        //创建临时顺序节点，没有权限限制
        zooKeeper.create("/zk-test-ephemeral-", "1".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL,
                new DemoCallback(), "path2" );
        Thread.sleep(Integer.MAX_VALUE);
    }

    private static class DemoWatcher implements Watcher{
        public void process(WatchedEvent watchedEvent) {
            if(Event.KeeperState.SyncConnected == watchedEvent.getState()){
                countDownLatch.countDown();
            }
        }
    }

    private static class DemoCallback implements AsyncCallback.StringCallback {
        @Override
        public void processResult(int rc, String path, Object ctx, String name) {
            System.out.println("创建节点：[" + rc + ", " + path + ", " + ctx.toString() +
            ", 真实path：" + name + "]");
        }
    }
}
    • 异步方法回调接口参数说明
    参数名 描述
    rc 服务端响应码：0 创建成功；-4 客户端和服务端的链接断开；-110 节点已存在；-112 会话过期
    path 对应create方法中节点路径参数值
    ctx 接口调用时传如API的ctx，即对应异步create方法中的ctx参数
    name 创建成功后，对应节点的真是路径
    • 同步方法和异步方法比较
    1. 同步方法会阻塞线程，异步方法不会
    2. 同步会抛出异常，异步方法不会，异常信息是通过状态码的方式传递到回调函数中

    删除

    • 方法（删除时不支持递归删除，也就是说某个节点如果存在子节点，则不能删除）
    #同步删除
public void delete(String path, int version) throws InterruptedException, KeeperException
#异步删除
public void delete(String path, int version, VoidCallback cb, Object ctx)
    • 参数说明
    参数名 描述
    path 要删除的节点对应的path
    version 数据节点的版本号，乐观锁
    cb 异步删除时的回调函数
    ctx 回调函数的参数
    • 例子
    package com.banary.base;

import org.apache.zookeeper.*;

import java.util.concurrent.CountDownLatch;

public class DeleteDemo {

    private static CountDownLatch countDownLatch = new CountDownLatch(1);

    public static void main(String[] args) throws Exception{
        asyncDelete();
    }

    public static void syncDelete() throws Exception{
        ZooKeeper zooKeeper = new ZooKeeper("localhost:2181", 5000, new DemoWatcher());
        countDownLatch.await();
        String path = zooKeeper.create("/deleteDemo", "deleteDemo".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        Thread.sleep(10000);
        zooKeeper.delete(path, 0);
    }

    public static void asyncDelete() throws Exception{
        ZooKeeper zooKeeper = new ZooKeeper("localhost:2181", 5000, new DemoWatcher());
        countDownLatch.await();

        String path = zooKeeper.create("/deleteDemo", "deleteDemo".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        Thread.sleep(5000);
        zooKeeper.delete(path, 0, new DemoCallback(), "asyncDelete");
        Thread.sleep(5000);
    }

    private static class DemoWatcher implements Watcher{
        @Override
        public void process(WatchedEvent watchedEvent) {
            System.out.println("创建zk会话：" + watchedEvent.getState());
            if(Event.KeeperState.SyncConnected == watchedEvent.getState()){
                System.out.println("zk会话创建成功");
                countDownLatch.countDown();
            }
        }
    }

    public static class DemoCallback implements AsyncCallback.VoidCallback{
        @Override
        public void processResult(int rc, String path, Object ctx) {
            System.out.println("删除节点成功：[" + rc + ", " + path + ", " + ctx.toString() + "]");
        }
    }
}

    查询节点数据内容getData

    • 方法
    public byte[] getData(String path, Watcher watcher, Stat stat) throws KeeperException, InterruptedException
public byte[] getData(String path, boolean watch, Stat stat) throws KeeperException, InterruptedException
public void getData(String path, Watcher watcher, DataCallback cb, Object ctx)
public void getData(String path, boolean watch, DataCallback cb, Object ctx)
    • 参数
    参数名 描述
    path 要获取数据的节点的路径
    watcher 监听器
    watch true表示使用默认的监听器，即创建zk对象时注册的监听器
    stat 数据节点的状态信息，传入一个旧的stat变量，服务器响应后会用的新的stat变量替换
    cb 异步方法的回调函数
    ctx 回调函数上下文参数
    • 例子
    package com.banary.base;

import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;

import java.util.concurrent.CountDownLatch;

public class GetDataDemo {

    private static CountDownLatch countDownLatch = new CountDownLatch(1);

    public static void main(String[] args) throws Exception{
        asyncGetData();
    }

    /**
     * 同步获取数据
     * @throws Exception
     */
    public static void syncGetData() throws Exception{
        ZooKeeper zooKeeper = new ZooKeeper("localhost:2181", 5000, new DemoWatcher());
        countDownLatch.await();
        String path = zooKeeper.create("/syncGetData", "syncGetData".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
        System.out.println(new String(zooKeeper.getData(path,true, new Stat())));
    }

    /**
     * 异步获取数据
     */
    public static void asyncGetData() throws Exception{
        ZooKeeper zooKeeper = new ZooKeeper("localhost:2181", 5000, new DemoWatcher());
        countDownLatch.await();
        String path = zooKeeper.create("/asyncGetData", "asyncGetData".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
        System.out.println(new String(zooKeeper.getData(path,true, new Stat())));
        Thread.sleep(Integer.MAX_VALUE);
    }

    private static class DemoWatcher implements Watcher{
        @Override
        public void process(WatchedEvent watchedEvent) {
            if(Event.KeeperState.SyncConnected == watchedEvent.getState()){
                countDownLatch.countDown();
            }
        }
    }

    private static class DemoCallback implements AsyncCallback.DataCallback{
        @Override
        public void processResult(int rc, String path, Object ctx, byte[] bytes, Stat stat) {
            System.out.println("异步获取的数据内容为：" + new String(bytes));
        }
    }
}

    查询子节点getChildren

    • 方法
    public List<String> getChildren(String path, Watcher watcher) throws KeeperException, InterruptedException
public List<String> getChildren(String path, boolean watch) throws KeeperException, InterruptedException
public void getChildren(String path, Watcher watcher, ChildrenCallback cb, Object ctx)
public void getChildren(String path, boolean watch, ChildrenCallback cb, Object ctx)
public List<String> getChildren(String path, Watcher watcher, Stat stat) throws KeeperException, InterruptedException 
public List<String> getChildren(String path, boolean watch, Stat stat) throws KeeperException, InterruptedException
public void getChildren(String path, Watcher watcher, Children2Callback cb, Object ctx)
public void getChildren(String path, boolean watch, Children2Callback cb, Object ctx)
    • 参数
    参数名 描述
    path 要查询的节点
    watcher 注册一个监听器
    watch 使用默认的监听器
    cb 异步方法的回调函数
    ctx 回调函数上下文参数
    stat 闯入一个旧的Stat对象，查询后，会被服务端响应的新Stat对象替换

    修改

    • 方法
    #同步方法
public Stat setData(String path, byte[] data, int version) throws KeeperException, InterruptedException
#异步方法
public void setData(String path, byte[] data, int version, StatCallback cb, Object ctx)
    • 参数
    参数名 描述
    path 要修改的数据节点的路径
    data 修改后的数据
    version 数据修改时基于的版本号，即乐观锁
    cb 异步方法的回调函数
    ctx 回调函数上下文参数
    • 例子
    package com.banary.base;

import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;

import java.util.concurrent.CountDownLatch;

public class UpdateDemo {

    public static CountDownLatch countDownLatch = new CountDownLatch(1);

    public static void main(String[] args) throws Exception{
        asyncUpdate();
    }

    /**
     * 同步更新
     */
    public static void syncUpdate() throws Exception{
        ZooKeeper zooKeeper = new ZooKeeper("localhost:2181", 5000, new DemoWatcher());
        countDownLatch.await();
        String path = zooKeeper.create("/syncUpdate", "syncUpdate".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
        Stat stat = new Stat();
        System.out.println(new String(zooKeeper.getData(path, true, stat)));
        System.out.println(stat.getCzxid() + "," + stat.getMzxid() + "," + stat.getVersion());
        //-1 表示不加乐观锁
        zooKeeper.setData(path, "32123".getBytes(), -1);
        System.out.println(new String(zooKeeper.getData(path, true, stat)));
        System.out.println(stat.getCzxid() + "," + stat.getMzxid() + "," + stat.getVersion());
    }

    /**
     * 异步更新
     * @throws Exception
     */
    public static void asyncUpdate() throws Exception{
        ZooKeeper zooKeeper = new ZooKeeper("localhost:2181", 5000, new DemoWatcher());
        countDownLatch.await();

        String path = zooKeeper.create("/asyncUpdate", "asyncUpdate".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
        Stat stat = new Stat();
        System.out.println(new String(zooKeeper.getData(path, true, stat)));
        System.out.println(stat.getCzxid() + "," + stat.getMzxid() + "," + stat.getVersion());

        zooKeeper.setData(path, "dsadsa".getBytes(), -1, new DemoCallback(), "回调");
        Thread.sleep(Integer.MAX_VALUE);
    }

    private static class DemoWatcher implements Watcher{
        @Override
        public void process(WatchedEvent watchedEvent) {
            if(Event.KeeperState.SyncConnected == watchedEvent.getState()){
                countDownLatch.countDown();
            }else if(watchedEvent.getType() == Event.EventType.NodeDataChanged){
                System.out.println("节点数据内容发生了变化");
            }
        }
    }

    private static class DemoCallback implements AsyncCallback.StatCallback{
        @Override
        public void processResult(int rc, String path, Object ctx, Stat stat) {
            System.out.println("修改节点：[" + rc + ", " + path + ", " + ctx.toString() +
                    ", stat：" + stat.toString() + "]");
        }
    }
}

    判断节点是否存在

    • 方法
    public Stat exists(String path, Watcher watcher) throws KeeperException, InterruptedException
public Stat exists(String path, boolean watch) throws KeeperException, InterruptedException
public void exists(String path, Watcher watcher, StatCallback cb, Object ctx)
public void exists(String path, boolean watch, StatCallback cb, Object ctx)
    • 参数
    参数名 描述
    path 要判断的节点路径
    watcher 注册一个监听器，用来监听节点被创建，删除，更新
    watch 是否使用默认的监听器
    cb 异步方法的回调函数
    ctx 回调函数上下文参数
    • 例子
    package com.banary.base;

import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;

import java.util.concurrent.CountDownLatch;

public class ExistsNodeDemo {

    public static CountDownLatch countDownLatch = new CountDownLatch(1);

    public static void main(String[] args) throws Exception{
        asyncExists();
    }

    /**
     * 同步
     */
    public static void syncExists() throws Exception{
        ZooKeeper zooKeeper = new ZooKeeper("localhost:2181", 5000, new DemoWatcher());
        countDownLatch.await();
        //创建
        String path = zooKeeper.create("/syncExists", "syncExists".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
        Stat stat = zooKeeper.exists(path, true);
        System.out.println(stat.toString());
        //更新
        stat = zooKeeper.setData(path, "3213".getBytes(), -1);
        System.out.println(stat.toString());
        //删除
        zooKeeper.delete(path, -1);
        Thread.sleep(Integer.MAX_VALUE);
    }

    /**
     * 异步
     */
    public static void asyncExists() throws Exception{
        ZooKeeper zooKeeper = new ZooKeeper("localhost:2181", 5000, new DemoWatcher());
        countDownLatch.await();
        //创建
        String path = zooKeeper.create("/asyncExists", "asyncExists".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
        zooKeeper.exists(path, true, new DemoCallback(), "asyncExists");
        Thread.sleep(Integer.MAX_VALUE);
    }

    private static class DemoWatcher implements Watcher {
        @Override
        public void process(WatchedEvent watchedEvent) {
            if(Event.KeeperState.SyncConnected == watchedEvent.getState()){
                countDownLatch.countDown();
            }else if(Event.EventType.NodeCreated == watchedEvent.getType()){
                System.out.println("创建节点");
            }else if(Event.EventType.NodeDataChanged == watchedEvent.getType()){
                System.out.println("修改节点");
            }else if(Event.EventType.NodeDeleted == watchedEvent.getType()){
                System.out.println("删除节点");
            }
        }
    }

    public static class DemoCallback implements AsyncCallback.StatCallback{
        @Override
        public void processResult(int rc, String path, Object ctx, Stat stat) {
            System.out.println("[" + rc + ", " + path + ", " + ctx.toString() +
                    ", stat：" + stat.toString() + "]");
        }
    }
}

    权限控制

    • 方法
    #zk会话对象的方法
public void addAuthInfo(String scheme, byte[] auth)
    • 参数
    参数名 描述
    scheme 权限控制模式，枚举值：world,auth,digest,ip和super
    auth 权限信息
    • 例子
    package com.banary.base;

import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;

import java.util.concurrent.CountDownLatch;

public class AuthDemo {

    private static CountDownLatch countDownLatch = null;

    public static void main(String[] args) throws Exception{
        authCreate();
    }

    public static void authCreate() throws Exception{
        countDownLatch = new CountDownLatch(1);
        ZooKeeper zooKeeper = new ZooKeeper("localhost:2181", 5000, new DemoWatcher());
        countDownLatch.await();
        zooKeeper.addAuthInfo("digest", "auth".getBytes());

        String path = zooKeeper.create("/auth", "auth".getBytes(), ZooDefs.Ids.CREATOR_ALL_ACL, CreateMode.PERSISTENT);

        countDownLatch = new CountDownLatch(1);
        ZooKeeper zooKeeper2 = new ZooKeeper("localhost:2181", 5000, new DemoWatcher());
        countDownLatch.await();
        zooKeeper2.addAuthInfo("digest", "auth".getBytes());
        System.out.println(new String(zooKeeper2.getData(path, true, new Stat())));

        countDownLatch = new CountDownLatch(1);
        ZooKeeper zooKeeper1 = new ZooKeeper("localhost:2181", 5000, new DemoWatcher());
        countDownLatch.await();
        System.out.println(new String(zooKeeper1.getData(path, true, new Stat())));

    }

    private static class DemoWatcher implements Watcher {
        public void process(WatchedEvent watchedEvent) {
            if(Event.KeeperState.SyncConnected == watchedEvent.getState()){
                countDownLatch.countDown();
            }
        }
    }
}

    总结

    1. 除了创建会话是异步的，其他操作都存在同步和异步方法，同步会抛出异常
    2. 创建会话、查询（包括查询该节点的数据和子节点和判断节点存在）都可以注册监听器，也可以使用会话的默认监听器
  • 相关阅读:
    input输入框的各种样式
    Spring JdbcTemplate方法详解
    TF/IDF计算方法
    分布式日志收集系统--Chukwa
    分布式日志系统
    Iframe知识点
    拖拽事件
    面向对象知识点
    JS使用合并数组
    块元素block，内联元素inline; inline-block;
  • 原文地址：https://www.cnblogs.com/warking/p/7565532.html
Copyright © 2011-2022 走看看