Zookeeper客户端java代码操作
上篇博客记录了shell命令操作zookeeper集群的方式,这次尝试采用java代码来操作。通过查阅API,发现并不困难。
1. 首先获得客户端与服务器的连接
//zookeeper客户端
private ZooKeeper zkCli;
//连接地址
private static final String CONNECT_STRING = "hadoop102:2181,hadoop103:2181,hadoop104:2181";
//session过期时间
private static final int SESSION_TIMEOUT = 2000;
/**
* 创建客户端实例对象
*
* @throws IOException
*/
@Before
public void before() throws IOException {
zkCli = new ZooKeeper(CONNECT_STRING, SESSION_TIMEOUT, (event) -> {
System.out.println("默认的回调函数");
});
}
2. 列出根节点下的子节点(非递归)
@Test
public void ls() throws KeeperException, InterruptedException {
List<String> children = zkCli.getChildren("/", e -> {
System.out.println("自定义回调函数");
});
System.out.println("---------------------");
for (String child : children) {
System.out.println(child);
}
System.out.println("+++++++++++++++++++++");
Thread.sleep(Long.MAX_VALUE);
}
3. 在一个节点下创建子节点
@Test
public void create() throws KeeperException, InterruptedException {
//parameter1:创建的节点路径 parameter2:节点的数据 parameter3:节点权限 parameter4:节点类型
String str = zkCli.create("/idea", "idea2019".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
System.out.println(str);
Thread.sleep(Long.MAX_VALUE);
}
4. 获取指定节点的内容
@Test
public void get() throws KeeperException, InterruptedException {
byte[] data = zkCli.getData("/simon", true, new Stat());
String str = new String(data);
System.out.println(str);
}
5. 给指定节点设置值
@Test
public void set() throws KeeperException, InterruptedException {
Stat stat = zkCli.setData("/simon", "abcd".getBytes(), 1);
System.out.println(stat.getDataLength());
}
6. 获取指定节点的状态信息
@Test
public void stat() throws KeeperException, InterruptedException {
Stat exists = zkCli.exists("/ideaa", false);
if (exists == null) {
System.out.println("节点不存在");
} else {
System.out.println(exists.getDataLength());
}
}
7. 删除指定节点
@Test
public void delete() throws KeeperException, InterruptedException {
Stat exists = zkCli.exists("/idea", false);
if (exists != null) {
zkCli.delete("/idea", exists.getVersion());
}
}
8. 循环注册,动态获取节点的信息。
也就是当节点有任何变化时,就会调用回调函数,动态的显示节点的变化信息。
@Test
public void register() throws KeeperException, InterruptedException {
byte[] data = zkCli.getData("/simon2", new Watcher() {
@Override
public void process(WatchedEvent watchedEvent) {
try {
register();//发生事件,通知的时候在注册一遍,实现了循环调用
} catch (KeeperException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}, null);
System.out.println(new String(data));
}
@Test
public void testRegister() {
try {
register(); //调用register()方法,将进程卡住,循环执行register
Thread.sleep(Long.MAX_VALUE);
} catch (Exception e) {
e.printStackTrace();
}
}
代码很简单易懂,只是有些内部原理还是有些模糊,例如:Stat是什么?zookeeper是怎么监听到节点发生变化的?又是如何将变化通知给客户端的?在之后的博客中将会详细记录。~