一 curator简介:为了更好的实现java操作zookeeper服务器,后来出现Curator框架,非常的强大,目前已经是Apache的顶级项目,里面提供了更多丰富的操作,例如session超时重连、主从选举、分布式计数器、分布式锁等等适用于各种复杂的zookeeper场景的API封装。
maven依赖:
<dependency>
<groupld>org.apache.curator</groupld>
<artifactld>curator-framework</artifactld>
<version>2.4.2</version>
</dependency>
二 curator的使用:Curator框架中使用链式编程风格,易读性更强,使用工程方法创建连接对象。
1 使用CuratorFrameworkFactory的俩个静态工厂方法(参数不同)来实现:
参数1: connectString, 连接串
参数2: retryPolicy, 重试连接策略。有四种实现分别为:
ExponentialBackoffRetry
RetryNTimes
RetryOne Times
RetryUntilElapsed
参数3: sessionTimeoutMs 会话超时时间默认为60 000ms
参数4: connectionTimeoutMs 连接超时时间,默认为15 000ms
注意:对于retryPolicy策略通过一个接口来让用户自定义实现。
2 创建节点create方法,可选链式项:
creatingParentsIfNeeded
withMode
forPath
withACL 等
3 删除节点:delete方法,可选链式项:
deletingChildrenlfNeeded
guaranteed
withVersion
forPath 等
4 读取和修改数据getData、setData方法
5 异步绑定回调方法。比如创建节点时绑定一个回调函数,该回调函数可以输出服务器的状态码以及服务器事件类型。还可以加入一个线程池进行优化操作。
6 读取子节点方法:getChildren
7 判断节点是否存在方法:checkExists
三 使用curator监听功能:如果要使用类似Wather的监听功能Curator必须依赖-个jar包,
Maven依赖:
<dependency>
<groupld>org.apache.curator</groupld>
<artifactld>curator-recipes</artifactld>
<version>2.4.2</version>
</dependency>
有了这个依赖包,我们使用NodeCache的方式去客户端实例中注册一个 监听缓存,然后实现对应的监听方法即可。
这里我们主要有俩种监听方式:
NodeCacheListener:监听节点的新增、修改操作。
PathChildrenCacheListener:监听子节点的新增、修改、删除操作。
实例1.curator的使用
import org.apache.curator.RetryPolicy;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.recipes.cache.PathChildrenCache;
import org.apache.curator.framework.recipes.cache.PathChildrenCache.StartMode;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheEvent;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheListener;
import org.apache.curator.retry.ExponentialBackoffRetry;
public class CuratorWatcher2 {
/** zookeeper地址 */
static final String CONNECT_ADDR = "192.168.1.171:2181,192.168.1.172:2181,192.168.1.173:2181";
/** session超时时间 */
static final int SESSION_OUTTIME = 5000;//ms
public static void main(String[] args) throws Exception {
//1 重试策略:初试时间为1s 重试10次
RetryPolicy retryPolicy = new ExponentialBackoffRetry(1000, 10);
//2 通过工厂创建连接
CuratorFramework cf = CuratorFrameworkFactory.builder()
.connectString(CONNECT_ADDR)
.sessionTimeoutMs(SESSION_OUTTIME)
.retryPolicy(retryPolicy)
.build();
//3 建立连接
cf.start();
//4 建立一个PathChildrenCache缓存,第三个参数为是否接受节点数据内容 如果为false则不接受
PathChildrenCache cache = new PathChildrenCache(cf, "/super", true);
//5 在初始化的时候就进行缓存监听
cache.start(StartMode.POST_INITIALIZED_EVENT);
cache.getListenable().addListener(new PathChildrenCacheListener() {
/**
* <B>方法名称:</B>监听子节点变更<BR>
* <B>概要说明:</B>新建、修改、删除<BR>
* @see org.apache.curator.framework.recipes.cache.PathChildrenCacheListener#childEvent(org.apache.curator.framework.CuratorFramework, org.apache.curator.framework.recipes.cache.PathChildrenCacheEvent)
*/
@Override
public void childEvent(CuratorFramework cf, PathChildrenCacheEvent event) throws Exception {
switch (event.getType()) {
case CHILD_ADDED:
System.out.println("CHILD_ADDED :" + event.getData().getPath());
break;
case CHILD_UPDATED:
System.out.println("CHILD_UPDATED :" + event.getData().getPath());
break;
case CHILD_REMOVED:
System.out.println("CHILD_REMOVED :" + event.getData().getPath());
break;
default:
break;
}
}
});
//创建本身节点不发生变化
cf.create().forPath("/super", "init".getBytes());
//添加子节点
Thread.sleep(1000);
cf.create().forPath("/super/c1", "c1内容".getBytes());
Thread.sleep(1000);
cf.create().forPath("/super/c2", "c2内容".getBytes());
//修改子节点
Thread.sleep(1000);
cf.setData().forPath("/super/c1", "c1更新内容".getBytes());
//删除子节点
Thread.sleep(1000);
cf.delete().forPath("/super/c2");
//删除本身节点
Thread.sleep(1000);
cf.delete().deletingChildrenIfNeeded().forPath("/super");
Thread.sleep(Integer.MAX_VALUE);
}
}
实例2:NodeCacheListener 监听
import org.apache.curator.RetryPolicy;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.recipes.cache.NodeCache;
import org.apache.curator.framework.recipes.cache.NodeCacheListener;
import org.apache.curator.retry.ExponentialBackoffRetry;
public class CuratorWatcher1 {
/** zookeeper地址 */
static final String CONNECT_ADDR = "192.168.1.171:2181,192.168.1.172:2181,192.168.1.173:2181";
/** session超时时间 */
static final int SESSION_OUTTIME = 5000;//ms
public static void main(String[] args) throws Exception {
//1 重试策略:初试时间为1s 重试10次
RetryPolicy retryPolicy = new ExponentialBackoffRetry(1000, 10);
//2 通过工厂创建连接
CuratorFramework cf = CuratorFrameworkFactory.builder()
.connectString(CONNECT_ADDR)
.sessionTimeoutMs(SESSION_OUTTIME)
.retryPolicy(retryPolicy)
.build();
//3 建立连接
cf.start();
//4 建立一个cache缓存
final NodeCache cache = new NodeCache(cf, "/super", false);
cache.start(true);
cache.getListenable().addListener(new NodeCacheListener() {
/**
* <B>方法名称:</B>nodeChanged<BR>
* <B>概要说明:</B>触发事件为创建节点和更新节点,在删除节点的时候并不触发此操作。<BR>
* @see org.apache.curator.framework.recipes.cache.NodeCacheListener#nodeChanged()
*/
@Override
public void nodeChanged() throws Exception {
System.out.println("路径为:" + cache.getCurrentData().getPath());
System.out.println("数据为:" + new String(cache.getCurrentData().getData()));
System.out.println("状态为:" + cache.getCurrentData().getStat());
System.out.println("---------------------------------------");
}
});
Thread.sleep(1000);
cf.create().forPath("/super", "123".getBytes());
Thread.sleep(1000);
cf.setData().forPath("/super", "456".getBytes());
Thread.sleep(1000);
cf.delete().forPath("/super");
Thread.sleep(Integer.MAX_VALUE);
}
}
实例3:PathChildrenCacheListener
import org.apache.curator.RetryPolicy;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.recipes.cache.PathChildrenCache;
import org.apache.curator.framework.recipes.cache.PathChildrenCache.StartMode;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheEvent;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheListener;
import org.apache.curator.retry.ExponentialBackoffRetry;
public class CuratorWatcher2 {
/** zookeeper地址 */
static final String CONNECT_ADDR = "192.168.1.171:2181,192.168.1.172:2181,192.168.1.173:2181";
/** session超时时间 */
static final int SESSION_OUTTIME = 5000;//ms
public static void main(String[] args) throws Exception {
//1 重试策略:初试时间为1s 重试10次
RetryPolicy retryPolicy = new ExponentialBackoffRetry(1000, 10);
//2 通过工厂创建连接
CuratorFramework cf = CuratorFrameworkFactory.builder()
.connectString(CONNECT_ADDR)
.sessionTimeoutMs(SESSION_OUTTIME)
.retryPolicy(retryPolicy)
.build();
//3 建立连接
cf.start();
//4 建立一个PathChildrenCache缓存,第三个参数为是否接受节点数据内容 如果为false则不接受
PathChildrenCache cache = new PathChildrenCache(cf, "/super", true);
//5 在初始化的时候就进行缓存监听
cache.start(StartMode.POST_INITIALIZED_EVENT);
cache.getListenable().addListener(new PathChildrenCacheListener() {
/**
* <B>方法名称:</B>监听子节点变更<BR>
* <B>概要说明:</B>新建、修改、删除<BR>
* @see org.apache.curator.framework.recipes.cache.PathChildrenCacheListener#childEvent(org.apache.curator.framework.CuratorFramework, org.apache.curator.framework.recipes.cache.PathChildrenCacheEvent)
*/
@Override
public void childEvent(CuratorFramework cf, PathChildrenCacheEvent event) throws Exception {
switch (event.getType()) {
case CHILD_ADDED:
System.out.println("CHILD_ADDED :" + event.getData().getPath());
break;
case CHILD_UPDATED:
System.out.println("CHILD_UPDATED :" + event.getData().getPath());
break;
case CHILD_REMOVED:
System.out.println("CHILD_REMOVED :" + event.getData().getPath());
break;
default:
break;
}
}
});
//创建本身节点不发生变化
cf.create().forPath("/super", "init".getBytes());
//添加子节点
Thread.sleep(1000);
cf.create().forPath("/super/c1", "c1内容".getBytes());
Thread.sleep(1000);
cf.create().forPath("/super/c2", "c2内容".getBytes());
//修改子节点
Thread.sleep(1000);
cf.setData().forPath("/super/c1", "c1更新内容".getBytes());
//删除子节点
Thread.sleep(1000);
cf.delete().forPath("/super/c2");
//删除本身节点
Thread.sleep(1000);
cf.delete().deletingChildrenIfNeeded().forPath("/super");
Thread.sleep(Integer.MAX_VALUE);
}
}