前言
Zookeeper API共包含五个包，分别为：
- org.apache.zookeeper
- org.apache.zookeeper.data
- org.apache.zookeeper.server
- org.apache.zookeeper.server.quorum
- org.apache.zookeeper.server.upgrade
其中org.apache.zookeeper，包含Zookeeper类，他是我们编程时最常⽤的类文件。这个类是Zookeeper客户端的主要类文件。如果要使用Zookeeper服务，应⽤程序⾸先必须创建⼀个Zookeeper实例，这时就需要使用此类。⼀旦客户端和Zookeeper服务端建立起了连接，Zookeeper系统将会给本次连接会话分配⼀个ID值，并且客户端将会周期性的向服务器端发送心跳来维持会话连接。只要连接有效，客户端就可以使⽤Zookeeper API来做相应处理了
导入依赖
org.apache.zookeeper zookeeper 3.4.14
建立会话
package com.lagou.api;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import java.io.IOException;
import java.util.concurrent.CountDownLatch;
public class CreateSession implements Watcher {
private static CountDownLatch countDownLatch = new CountDownLatch(1);
/**
* 建立会话
*/
public static void main(String[] args) throws IOException, InterruptedException {
/*
客户端可以通过创建⼀个zk实例来连接zk服务器
new Zookeeper(connectString,sesssionTimeOut,Wather)
connectString: 连接地址：IP：端⼝
sesssionTimeOut：会话超时时间：单位毫秒
Wather：监听器(当特定事件触发监听时，zk会通过watcher通知到客户端)
*/
ZooKeeper zooKeeper = new ZooKeeper("127.0.0.1:2181", 5000, new CreateSession());
System.out.println(zooKeeper.getState());
// 计数工具类 CountDownLatch : 不让main方法结束，让线程处于等待阻塞
countDownLatch.await();
System.out.println("客户端与服务端会话真正建立了");
}
/**
* 回调方法：处理来自服务器端的watcher通知
*/
// 当前类实现了Watcher接⼝，重写了process⽅法，该⽅法负责处理来⾃Zookeeper服务端的watcher通知，在收到服务端发送过来的SyncConnected事件之后，解除主程序在CountDownLatch上的等待阻塞，⾄此，会话创建完毕
public void process(WatchedEvent watchedEvent) {
//当连接创建了，服务端发送给客户端SyncConnected事件
if(watchedEvent.getState() == Event.KeeperState.SyncConnected) {
// 解除主程序在CountDownLatch上的等待阻塞
countDownLatch.countDown();
}
}
}
注意，ZooKeeper 客户端和服务端会话的建立是⼀个异步的过程，也就是说在程序中，构造⽅法会在处理完客户端初始化工作后立即返回，在⼤多数情况下，此时并没有真正建立好⼀个可用的会话，在会话的生命周期中处于“CONNECTING”的状态。当该会话真正创建完毕后ZooKeeper服务端会向会话对应的客户端发送⼀个事件通知，以告知客户端，客户端只有在获取这个通知之后，才算真正建立了会话。
创建节点
package com.lagou.api;
import org.apache.zookeeper.*;
import java.io.IOException;
import java.util.concurrent.CountDownLatch;
public class CreateNote implements Watcher {
private static ZooKeeper zooKeeper;
/**
* 建立会话
*/
public static void main(String[] args) throws IOException, InterruptedException, KeeperException {
/*
客户端可以通过创建⼀个zk实例来连接zk服务器
new Zookeeper(connectString,sesssionTimeOut,Wather)
connectString: 连接地址：IP：端⼝
sesssionTimeOut：会话超时时间：单位毫秒
Wather：监听器(当特定事件触发监听时，zk会通过watcher通知到客户端)
*/
zooKeeper = new ZooKeeper("127.0.0.1:2181", 5000, new CreateNote());
System.out.println(zooKeeper.getState());
Thread.sleep(Integer.MAX_VALUE);
}
// 创建节点的方法
private static void createNoteSync() throws InterruptedException, KeeperException {
/**
* path ：节点创建的路径
* data[] ：节点创建要保存的数据，是个byte类型的
* acl ：节点创建的权限信息(4种类型)
* ANYONE_ID_UNSAFE : 表示任何⼈
* AUTH_IDS ：此ID仅可⽤于设置ACL。它将被客户机验证的ID替换。
* OPEN_ACL_UNSAFE ：这是⼀个完全开放的ACL(常⽤)--> world:anyone
* CREATOR_ALL_ACL ：此ACL授予创建者身份验证ID的所有权限
* createMode ：创建节点的类型(4种类型)
* PERSISTENT：持久节点
* PERSISTENT_SEQUENTIAL：持久顺序节点
* EPHEMERAL：临时节点
* EPHEMERAL_SEQUENTIAL：临时顺序节点
String node = zookeeper.create(path,data,acl,createMode);
*/
// 持久节点
String note_persistent = zooKeeper.create("/lg-persistent", "持久节点内容".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
// 临时节点
String note_ephemeral = zooKeeper.create("/lg-ephemeral", "临时节点内容".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
// 持久顺序节点
String note_sequential = zooKeeper.create("/lg-sequential", "持久顺序节点内容".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT_SEQUENTIAL);
System.out.println("创建的持久节点: " + note_persistent);
System.out.println("创建的临时节点: " + note_ephemeral);
System.out.println("创建的持久顺序节点: " + note_sequential);
}
/**
* 回调方法：处理来自服务器端的watcher通知
*/
public void process(WatchedEvent watchedEvent) {
// SyncConnected
if (watchedEvent.getState() == Event.KeeperState.SyncConnected) {
// 创建节点
try {
createNoteSync();
} catch (Exception e) {
throw new RuntimeException(e);
}
}
}
}
获取节点数据
package com.lagou.api;
import org.apache.zookeeper.*;
import java.io.IOException;
import java.util.List;
public class GetNoteData implements Watcher {
private static ZooKeeper zooKeeper;
/**
* 建立会话
*/
public static void main(String[] args) throws IOException, InterruptedException, KeeperException {
/*
客户端可以通过创建⼀个zk实例来连接zk服务器
new Zookeeper(connectString,sesssionTimeOut,Wather)
connectString: 连接地址：IP：端⼝
sesssionTimeOut：会话超时时间：单位毫秒
Wather：监听器(当特定事件触发监听时，zk会通过watcher通知到客户端)
*/
zooKeeper = new ZooKeeper("127.0.0.1:2181", 5000, new GetNoteData());
System.out.println(zooKeeper.getState());
Thread.sleep(Integer.MAX_VALUE);
}
/**
* 回调方法：处理来自服务器端的watcher通知
*/
public void process(WatchedEvent watchedEvent) {
/*
子节点列表发生改变时，服务端会发送noteChildrenChanged事件通知
要重新获取子节点列表，同时注意：通知是一次性的，需要反复注册监听
*/
if (watchedEvent.getType() == Event.EventType.NodeChildrenChanged) {
List children = null;
try {
children = zooKeeper.getChildren("/lg-persistent", true);
} catch (KeeperException | InterruptedException e) {
throw new RuntimeException(e);
}
System.out.println(children);
}
// SyncConnected
if (watchedEvent.getState() == Event.KeeperState.SyncConnected) {
// 获取节点数据的方法
try {
getNoteData();
// 获取节点的子节点列表方法
getChildren();
} catch (Exception e) {
throw new RuntimeException(e);
}
}
}
/*
获取某个节点的内容
*/
private void getNoteData() throws Exception {
/**
* path : 获取数据的路径
* watch : 是否开启监听
* stat : 节点状态信息
* null: 表示获取最新版本的数据
* zk.getData(path, watch, stat);
*/
byte[] data = zooKeeper.getData("/lg-persistent", false, null);
System.out.println(new String(data));
}
/*
获取某个节点的子节点列表方法
*/
public static void getChildren() throws InterruptedException, KeeperException {
/*
path:路径
watch:是否要启动监听，当⼦节点列表发⽣变化，会触发监听
zooKeeper.getChildren(path, watch);
*/
List children = zooKeeper.getChildren("/lg-persistent", true);
System.out.println(children);
}
}
修改节点数据
package com.lagou.api;
import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;
import java.io.IOException;
public class UpdateNoteData implements Watcher {
private static ZooKeeper zooKeeper;
/**
* 建立会话
*/
public static void main(String[] args) throws IOException, InterruptedException, KeeperException {
/*
客户端可以通过创建⼀个zk实例来连接zk服务器
new Zookeeper(connectString,sesssionTimeOut,Wather)
connectString: 连接地址：IP：端⼝
sesssionTimeOut：会话超时时间：单位毫秒
Wather：监听器(当特定事件触发监听时，zk会通过watcher通知到客户端)
*/
zooKeeper = new ZooKeeper("127.0.0.1:2181", 5000, new UpdateNoteData());
System.out.println(zooKeeper.getState());
Thread.sleep(Integer.MAX_VALUE);
}
/**
* 回调方法：处理来自服务器端的watcher通知
*/
public void process(WatchedEvent watchedEvent) {
// SyncConnected
if (watchedEvent.getState() == Event.KeeperState.SyncConnected) {
// 更新数据节点内容的方法
try {
updateNoteSync();
} catch (InterruptedException | KeeperException e) {
throw new RuntimeException(e);
}
}
}
/*
更新数据节点内容的方法
*/
private void updateNoteSync() throws InterruptedException, KeeperException {
/*
path:路径
data:要修改的内容 byte[]
version:为-1，表示对最新版本的数据进⾏修改
zooKeeper.setData(path, data,version);
*/
byte[] data = zooKeeper.getData("/lg-persistent", false, null);
System.out.println("修改前的值：" + new String(data));
// 修改 /lg-persistent 的数据 stat: 状态信息对象
Stat stat = zooKeeper.setData("/lg-persistent", "客户端修改了节点数据".getBytes(), -1);
byte[] data2 = zooKeeper.getData("/lg-persistent", false, null);
System.out.println("修改后的值：" + new String(data2));
}
}
删除节点
package com.lagou.api;
import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;
import java.io.IOException;
public class DeleteNote implements Watcher {
private static ZooKeeper zooKeeper;
/**
* 建立会话
*/
public static void main(String[] args) throws IOException, InterruptedException, KeeperException {
/*
客户端可以通过创建⼀个zk实例来连接zk服务器
new Zookeeper(connectString,sesssionTimeOut,Wather)
connectString: 连接地址：IP：端⼝
sesssionTimeOut：会话超时时间：单位毫秒
Wather：监听器(当特定事件触发监听时，zk会通过watcher通知到客户端)
*/
zooKeeper = new ZooKeeper("127.0.0.1:2181", 5000, new DeleteNote());
System.out.println(zooKeeper.getState());
Thread.sleep(Integer.MAX_VALUE);
}
/**
* 回调方法：处理来自服务器端的watcher通知
*/
public void process(WatchedEvent watchedEvent) {
// SyncConnected
if (watchedEvent.getState() == Event.KeeperState.SyncConnected) {
// 删除节点
try {
deleteNoteSync();
} catch (InterruptedException | KeeperException e) {
throw new RuntimeException(e);
}
}
}
/*
删除节点方法
*/
private void deleteNoteSync() throws InterruptedException, KeeperException {
/*
zooKeeper.exists(path,watch) :判断节点是否存在
zookeeper.delete(path,version) : 删除节点
*/
Stat stat = zooKeeper.exists("/lg-persistent/c1", false);
System.out.println(stat == null ? "该节点不存在" : "该节点存在");
if (stat != null) {
zooKeeper.delete("/lg-persistent/c1", -1);
}
Stat stat2 = zooKeeper.exists("/lg-persistent/c1", false);
System.out.println(stat2 == null ? "该节点不存在" : "该节点存在");
}
}
到此这篇关于分布式框架Zookeeper api的使用介绍的文章就介绍到这了,更多相关Zookeeper api内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家！