之前写过命令行的使用，如果没看过或者没记住的可以参考一下哈：
zookeeper系列之命令行讲解_阿小冰的博客-CSDN博客zookeeper系列之命令行讲解https://blog.csdn.net/qq_38377525/article/details/123326056咱们都是做JAVA开发的，所以对于代码集成ZK的API也是必不可少的，所以这里做一次API的使用记录
API介绍
zookeeper为多种语言都提供了API接口，那这里咱们主要讲一下JAVA的API使用，zookeeper的API主要是有五个包，分别是：
JAVA代码调用API 1、导入依赖1、org.apache.zookeeper：最主要的一个类，我们要使用zk服务，就必须要先创建一个zk的实例，就是要创建这个ZooKeeper类的实例
2、org.apache.zookeeper.data
3、org.apache.zookeeper.server
4、org.apache.zookeeper.server.quorum
5、org.apache.zookeeper.server.upgrade
org.apache.zookeeper zookeeper3.4.14
2、创建会话
public class CreateSession implements Watcher {
//为了不让main方法直接结束
private static CountDownLatch countDownLatch = new CountDownLatch(1);
public static void main(String[] args) throws IOException, InterruptedException {
ZooKeeper zooKeeper = new ZooKeeper(
"127.0.0.1:2181", //链接地址，IP：port
5000,//会话超时时间ms
new CreateSession());//监听器，当特定事件触发监听时，zk会通过watcher通知到客户端
System.out.println("zk当前状态是：" + zooKeeper.getState());
//线程等待
countDownLatch.await();
//打印，证明会话创建成功
System.out.println("session created");
}
@Override
public void process(WatchedEvent watchedEvent) {
//当创建链接后，服务端发送给客户端一个SunvConnected事件
if(watchedEvent.getState()==Event.KeeperState.SyncConnected){
//销毁线程
countDownLatch.countDown();
}
}
}
执行main方法，观察控制台打印：
说明会话已建立
3、创建节点
public class CreateNode implements Watcher {
//为了不让main方法直接结束
private static CountDownLatch countDownLatch = new CountDownLatch(1);
private static ZooKeeper zooKeeper;
public static void main(String[] args) throws IOException, InterruptedException {
zooKeeper = new ZooKeeper(
"127.0.0.1:2181", //链接地址，IP：port
5000,//会话超时事件ms
new CreateNode());//监听器，当特定事件出发监听时，zk会通过watcher通知到客户端
System.out.println("zk当前状态是：" + zooKeeper.getState());
//线程等待
countDownLatch.await();
//打印，证明会话创建成功
System.out.println("znode created");
}
@Override
public void process(WatchedEvent watchedEvent) {
//创建节点
try {
createNode();
}catch (Exception e) {
e.printStackTrace();
}
//当创建链接后，服务端发送给客户端一个SunvConnected事件
if (watchedEvent.getState() == Event.KeeperState.SyncConnected) {
//销毁线程
countDownLatch.countDown();
}
}
private void createNode() throws Exception{
String node_PERSISTENT = zooKeeper.create("/api_persistent", "持久节点的内容".getBytes("utf-8"), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
String node_PERSISTENT_SEQUENTIAL =
zooKeeper.create("/api_persistent_sequential", "持久顺序节点的内容".getBytes("utf-8"),
ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT_SEQUENTIAL);
String node_EPERSISTENT = zooKeeper.create("/api_ephemeral", "临时节点的内容".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
System.out.println("创建的持久节点是:" + node_PERSISTENT);
System.out.println("创建的持久顺序节点是:" + node_PERSISTENT_SEQUENTIAL);
System.out.println("创建的临时节点是:" + node_EPERSISTENT);
}
}
查看可视化工具是否真的创建成功：
三个api开头的节点，说明创建成功
4、获取节点数据
public class GetNode implements Watcher {
//为了不让main方法直接结束
private static CountDownLatch countDownLatch = new CountDownLatch(1);
private static ZooKeeper zooKeeper;
public static void main(String[] args) throws IOException, InterruptedException {
zooKeeper = new ZooKeeper(
"127.0.0.1:2181", //链接地址，IP：port
5000,//会话超时事件ms
new GetNode());//监听器，当特定事件出发监听时，zk会通过watcher通知到客户端
//线程等待
countDownLatch.await();
System.out.println("get success");
}
@Override
public void process(WatchedEvent watchedEvent) {
//⼦节点列表发⽣变化时，服务器会发出NodeChildrenChanged通知，但不会把变化情况告诉给客户端
// 需要客户端⾃⾏获取，且通知是⼀次性的，需反复注册监听
if(watchedEvent.getType() ==Event.EventType.NodeChildrenChanged){
//再次获取节点数据
try {
List children =
zooKeeper.getChildren(watchedEvent.getPath(), true);
System.out.println(children);
} catch (Exception e) {
e.printStackTrace();
}
}
if(watchedEvent.getState() == Event.KeeperState.SyncConnected){
try {
//调用获取单个节点数据方法
getNodeDate();
//获取子节点信息
getChildrens();
} catch (Exception e) {
e.printStackTrace();
}
}
}
private void getNodeDate() throws Exception {
byte[] data = zooKeeper.getData("/api_persistent", true, null);
System.out.println(new String(data, "utf-8"));
}
private static void getChildrens() throws KeeperException, InterruptedException {
List children = zooKeeper.getChildren("/api_persistent", true);
System.out.println(children);
}
}
查看日志：
说明成功，下面的[]是因为当前节点下无子节点信息，所以返回的[]
5、修改节点数据
public class UpdateNode implements Watcher {
private static CountDownLatch countDownLatch = new CountDownLatch(1);
private static ZooKeeper zooKeeper;
public static void main(String[] args) throws Exception {
zooKeeper = new ZooKeeper("127.0.0.1:2181", 5000, new UpdateNode());
countDownLatch.await();
}
public void process(WatchedEvent watchedEvent) {
try {
updateNodeSync();
} catch (Exception e) {
e.printStackTrace();
}
}
private void updateNodeSync() throws Exception {
byte[] data = zooKeeper.getData("/api_persistent", false, null);
System.out.println("修改前的值:" + new String(data));
//修改 stat:状态信息对象 -1:最新版本
Stat stat = zooKeeper.setData("/api_persistent", "客户端修改内容".getBytes(), -1);
byte[] data2 = zooKeeper.getData("/api_persistent", false, null);
System.out.println("修改后的值:" + new String(data2));
}
}
观察日志打印：
6、删除节点数据
删除之前看一下Znode Tree：
那我们来删除一下zk-create-s0000000002，代码如下：
public class DeleteNode implements Watcher {
private static CountDownLatch countDownLatch = new CountDownLatch(1);
private static ZooKeeper zooKeeper;
public static void main(String[] args) throws Exception {
zooKeeper = new ZooKeeper("127.0.0.1:2181", 5000, new DeleteNode());
countDownLatch.await();
}
public void process(WatchedEvent watchedEvent) {
//当连接创建了，服务端发送给客户端SyncConnected事件
try {
deleteNodeSync();
} catch (Exception e) {
e.printStackTrace();
}
}
private void deleteNodeSync() throws KeeperException, InterruptedException {
Stat exists = zooKeeper.exists("/zk-create-s0000000002", false);
System.out.println(exists == null ? "该节点不存在" : "该节点存在");
zooKeeper.delete("/zk-create-s0000000002", -1);
Stat exists2 = zooKeeper.exists("/zk-create-s0000000002", false);
System.out.println(exists2 == null ? "该节点不存在" : "该节点存在");
}
}
查看日志打印：
再查看一下可视化工具的内容：
刚才的zk-create-s0000000002已经被删除了
以上案例是直接使用ZooKeeper源码工具类直接操作，其实网上有很多开源的zk客户端工具类，帮我们封装了上面案例中的API，节省了比上面代码还要多的代码，用起来也很方便，大多数情况开发的时候都会用封装类，也就是ZkClient，这里就不做陈述了，只不过建议是先了解底层提供的API然后再去使用封装工具类，这样也不至于只会用不知底的情况
