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>
1. 原生客户端
1.1 创建会话
1.1.1 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
1.1.2 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
1.2 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();
}
}
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
1.3 watch机制
1.4 ZooKeeper认证机制
2. zkClient
2.1 基本操作
2.2 监听机制
3. curator
3.1 基本操作
3.2 监听机制