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
<dependency>
<groupId>org.apache.zookeeper</groupId>
<artifactId>zookeeper</artifactId>
<version>3.4.14</version>
</dependency>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<String> 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<String> 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Devmax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Devmax！