0 课程地址
https://coding.imooc.com/lesson/201.html#mid=12717
1 重点关注
1.1 本节内容
使用STS开发工具作为客户端连接zk服务端，详见3.1
1.2 连接方式参数说明
如下段zk原生class标注：
- connectString：
连接zk服务端的ip和端口（比如案例的 集群：127.0.0.1:3000,127.0.0.1:3001,127.0.0.1:3002，单机：172.26.139.4:2181）
- sessionTimeout：
session会话的超时时间
- watcher：
watcher事件
a 本类直接实现 Watcher接口，传入本类，然后再process方法写业务逻辑即可（process方法是Watcher接口的抽象方法，所以子类可以重写）。 详见3.1
b process方法入参 WatchedEvent 的属性 EventType 是枚举，可以判断事件类型，比如节点创建删除更改等，我已在下边标注对应的字典
- sessionId和sessionPasswd(不常用)
旧的session断开后，可以用这两个字段恢复旧的会话
- canBeReadOnly（不常用）
会话已经断开，原先会话的数据还是可以读取（因为断开连接了，原数据可能已经不是最新的了，读取的可能数据不一致，所以通常不用或者设置为false）
/** * * * @param connectString * comma separated host:port pairs, each corresponding to a zk * server. e.g. "127.0.0.1:3000,127.0.0.1:3001,127.0.0.1:3002" * If the optional chroot suffix is used the example would look * like: "127.0.0.1:3000,127.0.0.1:3001,127.0.0.1:3002/app/a" * where the client would be rooted at "/app/a" and all paths * would be relative to this root - ie getting/setting/etc... * "/foo/bar" would result in operations being run on * "/app/a/foo/bar" (from the server perspective). * @param sessionTimeout * session timeout in milliseconds * @param watcher * a watcher object which will be notified of state changes, may * also be notified for node events * @param sessionId * specific session id to use if reconnecting * @param sessionPasswd * password for this session * @param canBeReadOnly * (added in 3.4) whether the created client is allowed to go to * read-only mode in case of partitioning. Read-only mode * basically means that if the client can't find any majority * servers but there's partitioned server it could reach, it * connects to one in read-only mode, i.e. read requests are * allowed while write requests are not. It continues seeking for * majority in the background. * * @throws IOException in cases of network failure * @throws IllegalArgumentException if an invalid chroot path is specified */ public ZooKeeper(String connectString, int sessionTimeout, Watcher watcher, long sessionId, byte[] sessionPasswd, boolean canBeReadOnly) throws IOException { LOG.info("Initiating client connection, connectString=" + connectString + " sessionTimeout=" + sessionTimeout + " watcher=" + watcher + " sessionId=" + Long.toHexString(sessionId) + " sessionPasswd=" + (sessionPasswd == null ? "<null>" : "<hidden>")); watchManager.defaultWatcher = watcher; ConnectStringParser connectStringParser = new ConnectStringParser( connectString); HostProvider hostProvider = new StaticHostProvider( connectStringParser.getServerAddresses()); cnxn = new ClientCnxn(connectStringParser.getChrootPath(), hostProvider, sessionTimeout, this, watchManager, getClientCnxnSocket(), sessionId, sessionPasswd, canBeReadOnly); cnxn.seenRwServerBefore = true; // since user has provided sessionId cnxn.start(); }
None (-1), NodeCreated (1), NodeDeleted (2), NodeDataChanged (3), NodeChildrenChanged (4);
2 课程内容
2.1 STS下载安装
- 下载链接:STS下载地址
- 直接点击下载即可;
- 直接解压文件即可使用;
- 双击STS打开工具
参考：
https://blog.csdn.net/qq_42139049/article/details/129034837
3 Coding
3.1 通过STS连接zk服务端
- 主类：
package com.imooc.zk.demo; import java.util.concurrent.CountDownLatch; import org.apache.zookeeper.WatchedEvent; import org.apache.zookeeper.Watcher; import org.apache.zookeeper.ZooKeeper; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * @Title: ZKConnectDemo.java * @Package com.imooc.zk.demo * @Description: zookeeper 连接demo演示 */ public class ZKConnect implements Watcher { final static Logger log = LoggerFactory.getLogger(ZKConnect.class); public static final String zkServerPath = "172.26.139.4:2181"; // public static final String zkServerPath = "192.168.1.111:2181,192.168.1.111:2182,192.168.1.111:2183"; public static final Integer timeout = 5000; public static void main(String[] args) throws Exception { /** * 客户端和zk服务端链接是一个异步的过程 * 当连接成功后后，客户端会收的一个watch通知 * * 参数： * connectString：连接服务器的ip字符串， * 比如: "192.168.1.1:2181,192.168.1.2:2181,192.168.1.3:2181" * 可以是一个ip，也可以是多个ip，一个ip代表单机，多个ip代表集群 * 也可以在ip后加路径 * sessionTimeout：超时时间，心跳收不到了，那就超时 * watcher：通知事件，如果有对应的事件触发，则会收到一个通知；如果不需要，那就设置为null * canBeReadOnly：可读，当这个物理机节点断开后，还是可以读到数据的，只是不能写， * 此时数据被读取到的可能是旧数据，此处建议设置为false，不推荐使用 * sessionId：会话的id * sessionPasswd：会话密码 当会话丢失后，可以依据 sessionId 和 sessionPasswd 重新获取会话 */ ZooKeeper zk = new ZooKeeper(zkServerPath, timeout, new ZKConnect()); log.warn("客户端开始连接zookeeper服务器..."); log.warn("连接状态：{}", zk.getState()); new Thread().sleep(2000); log.warn("连接状态：{}", zk.getState()); } @Override public void process(WatchedEvent event) { log.warn("接受到watch通知：{}", event); } }
- log4j.properties
log4j.rootLogger=WARN,console
log4j.appender.console=org.apache.log4j.ConsoleAppender
log4j.appender.console.encoding=UTF-8
log4j.appender.console.layout=org.apache.log4j.PatternLayout
log4j.appender.console.layout.ConversionPattern=%-d{yyyy-MM-dd HH:mm:ss,SSS} [%t] [%l] - [%p] %m%n
- 打印日志：
可见，已经打印出了process方法的内容
2024-03-29 07:30:34,843 [main] [com.imooc.zk.demo.ZKConnect.main(ZKConnect.java:43)] - [WARN] 客户端开始连接zookeeper服务器... 2024-03-29 07:30:34,848 [main] [com.imooc.zk.demo.ZKConnect.main(ZKConnect.java:44)] - [WARN] 连接状态：CONNECTING 2024-03-29 07:30:34,880 [main-EventThread] [com.imooc.zk.demo.ZKConnect.process(ZKConnect.java:53)] - [WARN] 接受到watch通知：WatchedEvent state:SyncConnected type:None path:null 2024-03-29 07:30:36,859 [main] [com.imooc.zk.demo.ZKConnect.main(ZKConnect.java:48)] - [WARN] 连接状态：CONNECTED
诸葛
