Zookeeper Java 客户端 ——Apache Curator
This commit is contained in:
罗祥
parent
75c92fdb48
commit
47b4eef1a2
@ -1,5 +1,6 @@
|
||||
# Zookeeper Java 客户端 ——Apache Curator
|
||||
<nav>
|
||||
# Zookeeper Java 客户端 ——Apache Curator
|
||||
|
||||
<nav>
|
||||
<a href="#一基本依赖">一、基本依赖</a><br/>
|
||||
<a href="#二客户端相关操作">二、客户端相关操作</a><br/>
|
||||
<a href="#21-创建客户端实例">2.1 创建客户端实例</a><br/>
|
||||
@ -18,317 +19,318 @@
|
||||
<a href="#33-监听子节点">3.3 监听子节点</a><br/>
|
||||
</nav>
|
||||
|
||||
## 一、基本依赖
|
||||
|
||||
Curator是Netflix公司开源的一个Zookeeper客户端，目前由Apache进行维护。与Zookeeper原生客户端相比，Curator的抽象层次更高，功能也更加丰富，是Zookeeper使用范围最广的Java客户端。本片文章主要讲解其基本使用，以下项目采用Maven构建，以单元测试的方法进行讲解，相关依赖如下：
|
||||
|
||||
```xml
|
||||
<dependencies>
|
||||
<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>
|
||||
<dependency>
|
||||
<groupId>org.apache.zookeeper</groupId>
|
||||
<artifactId>zookeeper</artifactId>
|
||||
<version>3.4.13</version>
|
||||
</dependency>
|
||||
<!--单元测试相关依赖-->
|
||||
<dependency>
|
||||
<groupId>junit</groupId>
|
||||
<artifactId>junit</artifactId>
|
||||
<version>4.12</version>
|
||||
</dependency>
|
||||
</dependencies>
|
||||
```
|
||||
|
||||
> 完整源码见本仓库： https://github.com/heibaiying/BigData-Notes/tree/master/code/Zookeeper/curator
|
||||
|
||||
|
||||
|
||||
## 二、客户端相关操作
|
||||
|
||||
### 2.1 创建客户端实例
|
||||
|
||||
这里使用`@Before`在单元测试执行前创建客户端实例，并使用`@After`在单元测试后关闭客户端连接。
|
||||
|
||||
```java
|
||||
public class BasicOperation {
|
||||
|
||||
private CuratorFramework client = null;
|
||||
private static final String zkServerPath = "192.168.0.226:2181";
|
||||
private static final String nodePath = "/hadoop/yarn";
|
||||
|
||||
@Before
|
||||
public void prepare() {
|
||||
// 重试策略
|
||||
RetryPolicy retryPolicy = new RetryNTimes(3, 5000);
|
||||
client = CuratorFrameworkFactory.builder()
|
||||
.connectString(zkServerPath)
|
||||
.sessionTimeoutMs(10000).retryPolicy(retryPolicy)
|
||||
.namespace("workspace").build(); //指定命名空间后，client的所有路径操作都会以/workspace开头
|
||||
client.start();
|
||||
}
|
||||
|
||||
@After
|
||||
public void destroy() {
|
||||
if (client != null) {
|
||||
client.close();
|
||||
}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
### 2.2 重试策略
|
||||
|
||||
在连接Zookeeper服务时候，Curator提供了多种重试策略以满足各种需求，所有重试策略继承自`RetryPolicy`接口，如下图：
|
||||
|
||||
<div align="center"> <img src="https://github.com/heibaiying/BigData-Notes/blob/master/pictures/curator-retry-policy.png"/> </div>
|
||||
|
||||
而这些重试策略类又分为两大类别：
|
||||
|
||||
+ RetryForever ：代表一直重试，直到连接成功；
|
||||
+ SleepingRetry ： 基于一定间隔时间的重试，这里以其子类`ExponentialBackoffRetry`为例说明，其构造器如下：
|
||||
|
||||
```java
|
||||
/**
|
||||
* @param baseSleepTimeMs 重试之间等待的初始时间
|
||||
* @param maxRetries 最大重试次数
|
||||
* @param maxSleepMs 每次重试间隔的最长睡眠时间（毫秒）
|
||||
*/
|
||||
ExponentialBackoffRetry(int baseSleepTimeMs, int maxRetries, int maxSleepMs)
|
||||
```
|
||||
### 2.3 判断服务状态
|
||||
|
||||
```scala
|
||||
@Test
|
||||
public void getStatus() {
|
||||
CuratorFrameworkState state = client.getState();
|
||||
System.out.println("服务是否已经启动:" + (state == CuratorFrameworkState.STARTED));
|
||||
}
|
||||
```
|
||||
|
||||
|
||||
|
||||
## 三、节点增删改查
|
||||
|
||||
### 3.1 创建节点
|
||||
|
||||
```java
|
||||
@Test
|
||||
public void createNodes() throws Exception {
|
||||
byte[] data = "abc".getBytes();
|
||||
client.create().creatingParentsIfNeeded()
|
||||
.withMode(CreateMode.PERSISTENT) //节点类型
|
||||
.withACL(ZooDefs.Ids.OPEN_ACL_UNSAFE)
|
||||
.forPath(nodePath, data);
|
||||
}
|
||||
```
|
||||
|
||||
创建时可以指定节点类型，这里的节点类型和Zookeeper原生的一致，全部定义在枚举类`CreateMode`中：
|
||||
|
||||
```java
|
||||
public enum CreateMode {
|
||||
// 永久节点
|
||||
PERSISTENT (0, false, false),
|
||||
//永久有序节点
|
||||
PERSISTENT_SEQUENTIAL (2, false, true),
|
||||
// 临时节点
|
||||
EPHEMERAL (1, true, false),
|
||||
// 临时有序节点
|
||||
EPHEMERAL_SEQUENTIAL (3, true, true);
|
||||
....
|
||||
}
|
||||
```
|
||||
|
||||
### 2.2 获取节点信息
|
||||
|
||||
```scala
|
||||
@Test
|
||||
public void getNode() throws Exception {
|
||||
Stat stat = new Stat();
|
||||
byte[] data = client.getData().storingStatIn(stat).forPath(nodePath);
|
||||
System.out.println("节点数据:" + new String(data));
|
||||
System.out.println("节点信息:" + stat.toString());
|
||||
}
|
||||
```
|
||||
|
||||
如上所示，节点信息被封装在`Stat`类中，其主要属性如下：
|
||||
|
||||
```java
|
||||
public class Stat implements Record {
|
||||
private long czxid;
|
||||
private long mzxid;
|
||||
private long ctime;
|
||||
private long mtime;
|
||||
private int version;
|
||||
private int cversion;
|
||||
private int aversion;
|
||||
private long ephemeralOwner;
|
||||
private int dataLength;
|
||||
private int numChildren;
|
||||
private long pzxid;
|
||||
...
|
||||
}
|
||||
```
|
||||
|
||||
每个属性的含义如下：
|
||||
|
||||
| **状态属性** | **说明** |
|
||||
| -------------- | ------------------------------------------------------------ |
|
||||
| czxid | 数据节点创建时的事务ID |
|
||||
| ctime | 数据节点创建时的时间 |
|
||||
| mzxid | 数据节点最后一次更新时的事务ID |
|
||||
| mtime | 数据节点最后一次更新时的时间 |
|
||||
| pzxid | 数据节点的子节点最后一次被修改时的事务ID |
|
||||
| cversion | 子节点的更改次数 |
|
||||
| version | 节点数据的更改次数 |
|
||||
| aversion | 节点的ACL的更改次数 |
|
||||
| ephemeralOwner | 如果节点是临时节点，则表示创建该节点的会话的SessionID；如果节点是持久节点，则该属性值为0 |
|
||||
| dataLength | 数据内容的长度 |
|
||||
| numChildren | 数据节点当前的子节点个数 |
|
||||
|
||||
### 2.3 获取子节点列表
|
||||
|
||||
```java
|
||||
@Test
|
||||
public void getChildrenNodes() throws Exception {
|
||||
List<String> childNodes = client.getChildren().forPath("/hadoop");
|
||||
for (String s : childNodes) {
|
||||
System.out.println(s);
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
### 2.4 更新节点
|
||||
|
||||
更新时可以传入版本号也可以不传入，如果传入则类似于乐观锁机制，只有在版本号正确的时候才会被更新。
|
||||
|
||||
```scala
|
||||
@Test
|
||||
public void updateNode() throws Exception {
|
||||
byte[] newData = "defg".getBytes();
|
||||
client.setData().withVersion(0) // 传入版本号，如果版本号错误则拒绝更新操作,并抛出BadVersion异常
|
||||
.forPath(nodePath, newData);
|
||||
}
|
||||
```
|
||||
|
||||
### 2.5 删除节点
|
||||
|
||||
```java
|
||||
@Test
|
||||
public void deleteNodes() throws Exception {
|
||||
client.delete()
|
||||
.guaranteed() // 如果删除失败，那么在会继续执行，直到成功
|
||||
.deletingChildrenIfNeeded() // 如果有子节点，则递归删除
|
||||
.withVersion(0) // 传入版本号，如果版本号错误则拒绝删除操作,并抛出BadVersion异常
|
||||
.forPath(nodePath);
|
||||
}
|
||||
```
|
||||
|
||||
### 2.6 判断节点是否存在
|
||||
|
||||
```java
|
||||
@Test
|
||||
public void existNode() throws Exception {
|
||||
// 如果节点存在则返回其状态信息如果不存在则为null
|
||||
Stat stat = client.checkExists().forPath(nodePath + "aa/bb/cc");
|
||||
System.out.println("节点是否存在:" + !(stat == null));
|
||||
}
|
||||
```
|
||||
|
||||
|
||||
|
||||
## 三、监听事件
|
||||
|
||||
### 3.1 创建一次性监听
|
||||
|
||||
和Zookeeper原生监听一样，使用`usingWatcher`注册的监听是一次性的，即监听只会触发一次，触发后就销毁。示例如下：
|
||||
|
||||
```java
|
||||
@Test
|
||||
public void DisposableWatch() throws Exception {
|
||||
client.getData().usingWatcher(new CuratorWatcher() {
|
||||
public void process(WatchedEvent event) {
|
||||
System.out.println("节点" + event.getPath() + "发生了事件:" + event.getType());
|
||||
}
|
||||
}).forPath(nodePath);
|
||||
Thread.sleep(1000 * 1000); //休眠以观察测试效果
|
||||
}
|
||||
```
|
||||
|
||||
### 3.2 创建永久监听
|
||||
|
||||
Curator还提供了创建永久监听的API，其使用方式如下：
|
||||
|
||||
```java
|
||||
@Test
|
||||
public void permanentWatch() throws Exception {
|
||||
// 使用NodeCache包装节点，对其注册的监听作用于节点，且是永久性的
|
||||
NodeCache nodeCache = new NodeCache(client, nodePath);
|
||||
// 通常设置为true, 代表创建nodeCache时,就去获取对应节点的值并缓存
|
||||
nodeCache.start(true);
|
||||
nodeCache.getListenable().addListener(new NodeCacheListener() {
|
||||
public void nodeChanged() {
|
||||
ChildData currentData = nodeCache.getCurrentData();
|
||||
if (currentData != null) {
|
||||
System.out.println("节点路径：" + currentData.getPath() +
|
||||
"数据：" + new String(currentData.getData()));
|
||||
}
|
||||
}
|
||||
});
|
||||
Thread.sleep(1000 * 1000); //休眠以观察测试效果
|
||||
}
|
||||
```
|
||||
|
||||
### 3.3 监听子节点
|
||||
|
||||
这里以监听`/hadoop`下所有子节点为例，实现方式如下：
|
||||
|
||||
```scala
|
||||
@Test
|
||||
public void permanentChildrenNodesWatch() throws Exception {
|
||||
|
||||
// 第三个参数代表除了节点状态外，是否还缓存节点内容
|
||||
PathChildrenCache childrenCache = new PathChildrenCache(client, "/hadoop", true);
|
||||
/*
|
||||
* StartMode代表初始化方式:
|
||||
* NORMAL: 异步初始化
|
||||
* BUILD_INITIAL_CACHE: 同步初始化
|
||||
* POST_INITIALIZED_EVENT: 异步并通知,初始化之后会触发INITIALIZED事件
|
||||
*/
|
||||
childrenCache.start(StartMode.POST_INITIALIZED_EVENT);
|
||||
|
||||
List<ChildData> childDataList = childrenCache.getCurrentData();
|
||||
System.out.println("当前数据节点的子节点列表：");
|
||||
childDataList.forEach(x -> System.out.println(x.getPath()));
|
||||
|
||||
childrenCache.getListenable().addListener(new PathChildrenCacheListener() {
|
||||
public void childEvent(CuratorFramework client, PathChildrenCacheEvent event) {
|
||||
switch (event.getType()) {
|
||||
case INITIALIZED:
|
||||
System.out.println("childrenCache初始化完成");
|
||||
break;
|
||||
case CHILD_ADDED:
|
||||
// 需要注意的是: 即使是之前已经存在的子节点，也会触发该监听，因为会把该子节点加入childrenCache缓存中
|
||||
System.out.println("增加子节点:" + event.getData().getPath());
|
||||
break;
|
||||
case CHILD_REMOVED:
|
||||
System.out.println("删除子节点:" + event.getData().getPath());
|
||||
break;
|
||||
case CHILD_UPDATED:
|
||||
System.out.println("被修改的子节点的路径:" + event.getData().getPath());
|
||||
System.out.println("修改后的数据:" + new String(event.getData().getData()));
|
||||
break;
|
||||
}
|
||||
}
|
||||
});
|
||||
Thread.sleep(1000 * 1000); //休眠以观察测试效果
|
||||
}
|
||||
## 一、基本依赖
|
||||
|
||||
Curator是Netflix公司开源的一个Zookeeper客户端，目前由Apache进行维护。与Zookeeper原生客户端相比，Curator的抽象层次更高，功能也更加丰富，是目前Zookeeper使用范围最广的Java客户端。本篇文章主要讲解其基本使用，项目采用Maven构建，以单元测试的方法进行讲解，相关依赖如下：
|
||||
|
||||
```xml
|
||||
<dependencies>
|
||||
<!--Curator相关依赖-->
|
||||
<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>
|
||||
<dependency>
|
||||
<groupId>org.apache.zookeeper</groupId>
|
||||
<artifactId>zookeeper</artifactId>
|
||||
<version>3.4.13</version>
|
||||
</dependency>
|
||||
<!--单元测试相关依赖-->
|
||||
<dependency>
|
||||
<groupId>junit</groupId>
|
||||
<artifactId>junit</artifactId>
|
||||
<version>4.12</version>
|
||||
</dependency>
|
||||
</dependencies>
|
||||
```
|
||||
|
||||
> 完整源码见本仓库： https://github.com/heibaiying/BigData-Notes/tree/master/code/Zookeeper/curator
|
||||
|
||||
|
||||
|
||||
## 二、客户端相关操作
|
||||
|
||||
### 2.1 创建客户端实例
|
||||
|
||||
这里使用`@Before`在单元测试执行前创建客户端实例，并使用`@After`在单元测试后关闭客户端连接。
|
||||
|
||||
```java
|
||||
public class BasicOperation {
|
||||
|
||||
private CuratorFramework client = null;
|
||||
private static final String zkServerPath = "192.168.0.226:2181";
|
||||
private static final String nodePath = "/hadoop/yarn";
|
||||
|
||||
@Before
|
||||
public void prepare() {
|
||||
// 重试策略
|
||||
RetryPolicy retryPolicy = new RetryNTimes(3, 5000);
|
||||
client = CuratorFrameworkFactory.builder()
|
||||
.connectString(zkServerPath)
|
||||
.sessionTimeoutMs(10000).retryPolicy(retryPolicy)
|
||||
.namespace("workspace").build(); //指定命名空间后，client的所有路径操作都会以/workspace开头
|
||||
client.start();
|
||||
}
|
||||
|
||||
@After
|
||||
public void destroy() {
|
||||
if (client != null) {
|
||||
client.close();
|
||||
}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
### 2.2 重试策略
|
||||
|
||||
在连接Zookeeper时，Curator提供了多种重试策略以满足各种需求，所有重试策略均继承自`RetryPolicy`接口，如下图：
|
||||
|
||||
<div align="center"> <img src="https://github.com/heibaiying/BigData-Notes/blob/master/pictures/curator-retry-policy.png"/> </div>
|
||||
|
||||
这些重试策略类主要分为以下两类：
|
||||
|
||||
+ **RetryForever** ：代表一直重试，直到连接成功；
|
||||
+ **SleepingRetry** ： 基于一定间隔时间的重试。这里以其子类`ExponentialBackoffRetry`为例说明，其构造器如下：
|
||||
|
||||
```java
|
||||
/**
|
||||
* @param baseSleepTimeMs 重试之间等待的初始时间
|
||||
* @param maxRetries 最大重试次数
|
||||
* @param maxSleepMs 每次重试间隔的最长睡眠时间（毫秒）
|
||||
*/
|
||||
ExponentialBackoffRetry(int baseSleepTimeMs, int maxRetries, int maxSleepMs)
|
||||
```
|
||||
### 2.3 判断服务状态
|
||||
|
||||
```scala
|
||||
@Test
|
||||
public void getStatus() {
|
||||
CuratorFrameworkState state = client.getState();
|
||||
System.out.println("服务是否已经启动:" + (state == CuratorFrameworkState.STARTED));
|
||||
}
|
||||
```
|
||||
|
||||
|
||||
|
||||
## 三、节点增删改查
|
||||
|
||||
### 3.1 创建节点
|
||||
|
||||
```java
|
||||
@Test
|
||||
public void createNodes() throws Exception {
|
||||
byte[] data = "abc".getBytes();
|
||||
client.create().creatingParentsIfNeeded()
|
||||
.withMode(CreateMode.PERSISTENT) //节点类型
|
||||
.withACL(ZooDefs.Ids.OPEN_ACL_UNSAFE)
|
||||
.forPath(nodePath, data);
|
||||
}
|
||||
```
|
||||
|
||||
创建时可以指定节点类型，这里的节点类型和Zookeeper原生的一致，全部类型定义在枚举类`CreateMode`中：
|
||||
|
||||
```java
|
||||
public enum CreateMode {
|
||||
// 永久节点
|
||||
PERSISTENT (0, false, false),
|
||||
//永久有序节点
|
||||
PERSISTENT_SEQUENTIAL (2, false, true),
|
||||
// 临时节点
|
||||
EPHEMERAL (1, true, false),
|
||||
// 临时有序节点
|
||||
EPHEMERAL_SEQUENTIAL (3, true, true);
|
||||
....
|
||||
}
|
||||
```
|
||||
|
||||
### 2.2 获取节点信息
|
||||
|
||||
```scala
|
||||
@Test
|
||||
public void getNode() throws Exception {
|
||||
Stat stat = new Stat();
|
||||
byte[] data = client.getData().storingStatIn(stat).forPath(nodePath);
|
||||
System.out.println("节点数据:" + new String(data));
|
||||
System.out.println("节点信息:" + stat.toString());
|
||||
}
|
||||
```
|
||||
|
||||
如上所示，节点信息被封装在`Stat`类中，其主要属性如下：
|
||||
|
||||
```java
|
||||
public class Stat implements Record {
|
||||
private long czxid;
|
||||
private long mzxid;
|
||||
private long ctime;
|
||||
private long mtime;
|
||||
private int version;
|
||||
private int cversion;
|
||||
private int aversion;
|
||||
private long ephemeralOwner;
|
||||
private int dataLength;
|
||||
private int numChildren;
|
||||
private long pzxid;
|
||||
...
|
||||
}
|
||||
```
|
||||
|
||||
每个属性的含义如下：
|
||||
|
||||
| **状态属性** | **说明** |
|
||||
| -------------- | ------------------------------------------------------------ |
|
||||
| czxid | 数据节点创建时的事务ID |
|
||||
| ctime | 数据节点创建时的时间 |
|
||||
| mzxid | 数据节点最后一次更新时的事务ID |
|
||||
| mtime | 数据节点最后一次更新时的时间 |
|
||||
| pzxid | 数据节点的子节点最后一次被修改时的事务ID |
|
||||
| cversion | 子节点的更改次数 |
|
||||
| version | 节点数据的更改次数 |
|
||||
| aversion | 节点的ACL的更改次数 |
|
||||
| ephemeralOwner | 如果节点是临时节点，则表示创建该节点的会话的SessionID；如果节点是持久节点，则该属性值为0 |
|
||||
| dataLength | 数据内容的长度 |
|
||||
| numChildren | 数据节点当前的子节点个数 |
|
||||
|
||||
### 2.3 获取子节点列表
|
||||
|
||||
```java
|
||||
@Test
|
||||
public void getChildrenNodes() throws Exception {
|
||||
List<String> childNodes = client.getChildren().forPath("/hadoop");
|
||||
for (String s : childNodes) {
|
||||
System.out.println(s);
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
### 2.4 更新节点
|
||||
|
||||
更新时可以传入版本号也可以不传入，如果传入则类似于乐观锁机制，只有在版本号正确的时候才会被更新。
|
||||
|
||||
```scala
|
||||
@Test
|
||||
public void updateNode() throws Exception {
|
||||
byte[] newData = "defg".getBytes();
|
||||
client.setData().withVersion(0) // 传入版本号，如果版本号错误则拒绝更新操作,并抛出BadVersion异常
|
||||
.forPath(nodePath, newData);
|
||||
}
|
||||
```
|
||||
|
||||
### 2.5 删除节点
|
||||
|
||||
```java
|
||||
@Test
|
||||
public void deleteNodes() throws Exception {
|
||||
client.delete()
|
||||
.guaranteed() // 如果删除失败，那么在会继续执行，直到成功
|
||||
.deletingChildrenIfNeeded() // 如果有子节点，则递归删除
|
||||
.withVersion(0) // 传入版本号，如果版本号错误则拒绝删除操作,并抛出BadVersion异常
|
||||
.forPath(nodePath);
|
||||
}
|
||||
```
|
||||
|
||||
### 2.6 判断节点是否存在
|
||||
|
||||
```java
|
||||
@Test
|
||||
public void existNode() throws Exception {
|
||||
// 如果节点存在则返回其状态信息如果不存在则为null
|
||||
Stat stat = client.checkExists().forPath(nodePath + "aa/bb/cc");
|
||||
System.out.println("节点是否存在:" + !(stat == null));
|
||||
}
|
||||
```
|
||||
|
||||
|
||||
|
||||
## 三、监听事件
|
||||
|
||||
### 3.1 创建一次性监听
|
||||
|
||||
和Zookeeper原生监听一样，使用`usingWatcher`注册的监听是一次性的，即监听只会触发一次，触发后就销毁。示例如下：
|
||||
|
||||
```java
|
||||
@Test
|
||||
public void DisposableWatch() throws Exception {
|
||||
client.getData().usingWatcher(new CuratorWatcher() {
|
||||
public void process(WatchedEvent event) {
|
||||
System.out.println("节点" + event.getPath() + "发生了事件:" + event.getType());
|
||||
}
|
||||
}).forPath(nodePath);
|
||||
Thread.sleep(1000 * 1000); //休眠以观察测试效果
|
||||
}
|
||||
```
|
||||
|
||||
### 3.2 创建永久监听
|
||||
|
||||
Curator还提供了创建永久监听的API，其使用方式如下：
|
||||
|
||||
```java
|
||||
@Test
|
||||
public void permanentWatch() throws Exception {
|
||||
// 使用NodeCache包装节点，对其注册的监听作用于节点，且是永久性的
|
||||
NodeCache nodeCache = new NodeCache(client, nodePath);
|
||||
// 通常设置为true, 代表创建nodeCache时,就去获取对应节点的值并缓存
|
||||
nodeCache.start(true);
|
||||
nodeCache.getListenable().addListener(new NodeCacheListener() {
|
||||
public void nodeChanged() {
|
||||
ChildData currentData = nodeCache.getCurrentData();
|
||||
if (currentData != null) {
|
||||
System.out.println("节点路径：" + currentData.getPath() +
|
||||
"数据：" + new String(currentData.getData()));
|
||||
}
|
||||
}
|
||||
});
|
||||
Thread.sleep(1000 * 1000); //休眠以观察测试效果
|
||||
}
|
||||
```
|
||||
|
||||
### 3.3 监听子节点
|
||||
|
||||
这里以监听`/hadoop`下所有子节点为例，实现方式如下：
|
||||
|
||||
```scala
|
||||
@Test
|
||||
public void permanentChildrenNodesWatch() throws Exception {
|
||||
|
||||
// 第三个参数代表除了节点状态外，是否还缓存节点内容
|
||||
PathChildrenCache childrenCache = new PathChildrenCache(client, "/hadoop", true);
|
||||
/*
|
||||
* StartMode代表初始化方式:
|
||||
* NORMAL: 异步初始化
|
||||
* BUILD_INITIAL_CACHE: 同步初始化
|
||||
* POST_INITIALIZED_EVENT: 异步并通知,初始化之后会触发INITIALIZED事件
|
||||
*/
|
||||
childrenCache.start(StartMode.POST_INITIALIZED_EVENT);
|
||||
|
||||
List<ChildData> childDataList = childrenCache.getCurrentData();
|
||||
System.out.println("当前数据节点的子节点列表：");
|
||||
childDataList.forEach(x -> System.out.println(x.getPath()));
|
||||
|
||||
childrenCache.getListenable().addListener(new PathChildrenCacheListener() {
|
||||
public void childEvent(CuratorFramework client, PathChildrenCacheEvent event) {
|
||||
switch (event.getType()) {
|
||||
case INITIALIZED:
|
||||
System.out.println("childrenCache初始化完成");
|
||||
break;
|
||||
case CHILD_ADDED:
|
||||
// 需要注意的是: 即使是之前已经存在的子节点，也会触发该监听，因为会把该子节点加入childrenCache缓存中
|
||||
System.out.println("增加子节点:" + event.getData().getPath());
|
||||
break;
|
||||
case CHILD_REMOVED:
|
||||
System.out.println("删除子节点:" + event.getData().getPath());
|
||||
break;
|
||||
case CHILD_UPDATED:
|
||||
System.out.println("被修改的子节点的路径:" + event.getData().getPath());
|
||||
System.out.println("修改后的数据:" + new String(event.getData().getData()));
|
||||
break;
|
||||
}
|
||||
}
|
||||
});
|
||||
Thread.sleep(1000 * 1000); //休眠以观察测试效果
|
||||
}
|
||||
```
|
||||
Loading…
x
Reference in New Issue
Block a user