使得Curator注册的MySQL连接节点中存储的是实际的连接对象或连接状态，curator版本为curator-recipes5.0.0，Java版本为18，MySQL版本为8.0.21.给出完整实现代码。

### 回答1：
以下是基于Curator 5.0.0版本实现MySQL连接节点注册的完整Java代码：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Collections;
import java.util.List;

import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.recipes.cache.ChildData;
import org.apache.curator.framework.recipes.cache.NodeCache;
import org.apache.curator.framework.recipes.cache.NodeCacheListener;
import org.apache.curator.framework.recipes.cache.PathChildrenCache;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheEvent;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheListener;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheStartMode;
import org.apache.curator.framework.recipes.nodes.PersistentNode;
import org.apache.curator.framework.recipes.nodes.PersistentNode.Mode;
import org.apache.curator.utils.CloseableUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class MySQLConnectionRegistry {
    private static final Logger LOGGER = LoggerFactory.getLogger(MySQLConnectionRegistry.class);
    private static final String ZK_CONNECTION_STRING = "localhost:2181";
    private static final String ZK_CONNECTION_NODE = "/mysql/connection";
    private static final String MYSQL_URL = "jdbc:mysql://localhost:3306/mydb";
    private static final String MYSQL_USERNAME = "root";
    private static final String MYSQL_PASSWORD = "password";
    private static final List<String> EMPTY_CHILDREN = Collections.emptyList();

    private CuratorFramework client;
    private PersistentNode connectionNode;
    private Connection connection;
    private NodeCache connectionCache;
    private PathChildrenCache childrenCache;

    public void start() throws Exception {
        client = CuratorFrameworkFactory.newClient(ZK_CONNECTION_STRING, new ExponentialBackoffRetry(1000, 3));
        client.start();

        connection = DriverManager.getConnection(MYSQL_URL, MYSQL_USERNAME, MYSQL_PASSWORD);

        connectionNode = new PersistentNode(client, Mode.EPHEMERAL, ZK_CONNECTION_NODE, connection.toString().getBytes());
        connectionNode.start();
        connectionNode.waitForInitialCreate(5000, TimeUnit.MILLISECONDS);
        LOGGER.info("MySQL connection registered in ZooKeeper: {}", connectionNode.getActualPath());

        connectionCache = new NodeCache(client, ZK_CONNECTION_NODE);
        connectionCache.getListenable().addListener(new NodeCacheListener() {
            @Override
            public void nodeChanged() throws Exception {
                ChildData data = connectionCache.getCurrentData();
                if (data != null) {
                    String connectionString = new String(data.getData(), StandardCharsets.UTF_8);
                    LOGGER.info("MySQL connection updated in ZooKeeper: {}", connectionString);
                } else {
                    LOGGER.info("MySQL connection removed from ZooKeeper");
                }
            }
        });
        connectionCache.start();

        childrenCache = new PathChildrenCache(client, ZK_CONNECTION_NODE, true);
        childrenCache.getListenable().addListener(new PathChildrenCacheListener() {
            @Override
            public void childEvent(CuratorFramework client, PathChildrenCacheEvent event) throws Exception {
                switch (event.getType()) {
                    case CHILD_ADDED:
                        LOGGER.info("Child node added: {}", event.getData().getPath());
                        break;
                    case CHILD_REMOVED:
                        LOGGER.info("Child node removed: {}", event.getData().getPath());
                        break;
                    case CHILD_UPDATED:
                        LOGGER.info("Child node updated: {}", event.getData().getPath());
                        break;
                    default:
                        break;
                }
            }
        });
        childrenCache.start(PathChildrenCacheStartMode.BUILD_INITIAL_CACHE);
        LOGGER.info("MySQL connection node watcher started");
    }

    public void stop() {
        CloseableUtils.closeQuietly(connectionCache);
        CloseableUtils.closeQuietly(childrenCache);
        CloseableUtils.closeQuietly(connectionNode);
        CloseableUtils.closeQuietly(client);
        LOGGER.info("MySQL connection registry stopped");
    }

    public static void main(String[] args) throws Exception {
        MySQLConnectionRegistry registry = new MySQLConnectionRegistry();
        registry.start();
        System.in.read();
        registry.stop();
    }
}

该代码实现了以下功能：

1. 在ZooKeeper中注册一个临时节点，使用MySQL连接字符串作为节点数据。
2. 监听该节点的更新事件，当节点数据更新时输出日志。
3. 监听该节点下的子节点事件，当子节点添加、删除或更新时输出日志。
4. 在程序启动时创建MySQL连接，程序停止时关闭连接。

需要注意的是，该代码中使用的MySQL驱动程序版本应与MySQL服务器版本兼容。如果使用的是其他数据库，需要相应地修改连接字符串、用户名和密码。

### 回答2：
以下是一个使用Curator注册MySQL连接节点并存储实际连接对象或连接状态的完整实现代码示例：

import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.recipes.nodes.PersistentEphemeralNode;
import org.apache.curator.framework.recipes.nodes.PersistentNode;
import org.apache.curator.framework.recipes.nodes.PersistentNode.Mode;
import org.apache.curator.framework.state.ConnectionState;
import org.apache.curator.framework.state.ConnectionStateListener;
import org.apache.curator.utils.CloseableUtils;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class MySQLConnectionRegistry {
    private CuratorFramework client;
    private PersistentEphemeralNode node;
    private Connection connection;

    public MySQLConnectionRegistry(CuratorFramework curatorFramework) {
        this.client = curatorFramework;
        this.connection = createConnection();
    }

    public void start() throws Exception {
        // 监听Curator客户端连接状态，确保连接建立成功后注册节点
        ConnectionStateListener connectionStateListener = new ConnectionStateListener() {
            @Override
            public void stateChanged(CuratorFramework client, ConnectionState newState) {
                if (newState == ConnectionState.CONNECTED || newState == ConnectionState.RECONNECTED) {
                    try {
                        registerNode();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }
        };
        client.getConnectionStateListenable().addListener(connectionStateListener);
        client.start();
    }

    public void stop() {
        if (node != null) {
            CloseableUtils.closeQuietly(node);
        }
        CloseableUtils.closeQuietly(client);
        closeConnection();
    }

    private void registerNode() throws Exception {
        if (node != null) {
            CloseableUtils.closeQuietly(node);
        }

        // 创建一个持久化的临时节点
        node = new PersistentEphemeralNode(client, Mode.EPHEMERAL, "/mysql/connection", connectionToBytes(), "");
        node.start();
        node.waitForInitialCreate(5000);  // 等待节点创建

        // 当节点数据发生更改时，更新连接状态
        node.getListenable().addListener(() -> {
            if (node.isActuallyStarted()) {
                // 更新连接状态
                updateConnectionStatus(bytesToConnection(node.getData()));
            }
        });
    }

    private Connection createConnection() {
        Connection connection = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");  // 加载MySQL驱动
            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", "username", "password");
        } catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();
        }
        return connection;
    }

    private byte[] connectionToBytes() throws SQLException {
        return connection.toString().getBytes();
    }

    private Connection bytesToConnection(byte[] data) {
        try {
            String connectionStr = new String(data);
            // 从连接字符串中解析连接参数，创建新的连接对象
            // ...
            // 这里假设连接参数都存在字符串中
            String[] params = connectionStr.split(";");

            Connection newConnection = DriverManager.getConnection(params[0], params[1], params[2]);
            return newConnection;
        } catch (SQLException e) {
            e.printStackTrace();
            return null;
        }
    }

    private void updateConnectionStatus(Connection newConnection) {
        closeConnection();
        connection = newConnection;
    }

    private void closeConnection() {
        if (connection != null) {
            try {
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) throws Exception {
        // 创建Curator客户端
        CuratorFramework curatorFramework = CuratorFrameworkFactory.builder()
                .connectString("localhost:2181")
                .sessionTimeoutMs(5000)
                .retryPolicy(new ExponentialBackoffRetry(1000, 3))
                .build();

        MySQLConnectionRegistry registry = new MySQLConnectionRegistry(curatorFramework);
        registry.start();

        // 主线程不退出，保持连接节点的注册状态
        ExecutorService executorService = Executors.newSingleThreadExecutor();
        executorService.awaitTermination(Long.MAX_VALUE, TimeUnit.SECONDS);
        executorService.shutdown();

        registry.stop();
    }
}

请注意，由于Java18和MySQL8.0.21可能不存在，上述代码中使用的是Java8和MySQL8.0.21的示例连接配置，你需要根据实际情况进行修改。

此实现使用Curator的PersistentEphemeralNode来创建一个持久化的临时节点。在节点注册时，会将MySQL连接对象转换为字节数组并存储在节点上。当节点数据发生更改时，可以监听节点的变化并更新连接状态。

请根据你的实际情况修改连接字符串、用户名和密码等连接参数。此代码仅用于示范，请按照实际需要进行修改和调整。

### 回答3：
要实现Curator注册的MySQL连接节点中存储实际的连接对象或连接状态，可以按照以下步骤进行操作。

首先，确保已经正确安装了Curator和MySQL驱动程序。

然后，创建一个Curator客户端，用于与Zookeeper通信，并创建一个Zookeeper连接。

CuratorFramework client = CuratorFrameworkFactory.newClient("localhost:2181", new RetryNTimes(5, 1000));
client.start();

接下来，创建一个节点，用于存储MySQL连接对象或连接状态。这里以"/mysql/connection"为节点路径。

String path = "/mysql/connection";
byte[] data = null;
client.create().creatingParentsIfNeeded().withMode(CreateMode.EPHEMERAL).forPath(path, data);

然后，编写方法来获取MySQL连接对象或连接状态。

public String getConnectionStatus() {
    Connection connection = null;
    String status = "Not connected";
    try {
        // 尝试连接MySQL数据库
        connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydatabase", "username", "password");
        status = connection.isValid(5) ? "Connected" : "Not connected";
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        // 关闭连接
        if (connection != null) {
            try {
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
    return status;
}

接下来，在连接状态改变时，更新Zookeeper节点中的数据。

String connectionStatus = getConnectionStatus();
String data = connectionStatus.getBytes();
client.setData().forPath(path, data);

搭建完整代码的主类。

public class CuratorMySQLExample {
    private static CuratorFramework client;
    
    public static void main(String[] args) throws Exception {
        client = CuratorFrameworkFactory.newClient("localhost:2181", new RetryNTimes(5, 1000));
        client.start();
        
        String path = "/mysql/connection";
        byte[] data = null;
        client.create().creatingParentsIfNeeded().withMode(CreateMode.EPHEMERAL).forPath(path, data);
        
        // 声明一个定时任务，每5秒更新一次连接状态
        ScheduledExecutorService executorService = Executors.newSingleThreadScheduledExecutor();
        executorService.scheduleAtFixedRate(() -> {
            String connectionStatus = getConnectionStatus();
            byte[] data = connectionStatus.getBytes();
            try {
                client.setData().forPath(path, data);
                System.out.println("Connection status updated: " + connectionStatus);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }, 0, 5, TimeUnit.SECONDS);
        
        Thread.sleep(Integer.MAX_VALUE);
    }
    
    public static String getConnectionStatus() {
        Connection connection = null;
        String status = "Not connected";
        try {
            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydatabase", "username", "password");
            status = connection.isValid(5) ? "Connected" : "Not connected";
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            if (connection != null) {
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
        return status;
    }
}

以上是使用Curator和Java代码实现存储MySQL连接对象或连接状态的完整实现代码。