mysql 分库

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

public class ShardingExample {
    public static void main(String[] args) {
        String userId = "12345";
        Connection conn = getDatabaseConnection(userId);
        if (conn != null) {
            try {
                String sql = "SELECT * FROM user WHERE id = ?";
                PreparedStatement ps = conn.prepareStatement(sql);
                ps.setString(1, userId);
                ResultSet rs = ps.executeQuery();
                while (rs.next()) {
                    System.out.println("User: " + rs.getString("name"));
                }
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                try {
                    conn.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }
    }

    private static Connection getDatabaseConnection(String userId) {
        String databaseUrl = "jdbc:mysql://db" + (userId.hashCode() % 3 + 1) + ".example.com:3306/mydb";
        try {
            return DriverManager.getConnection(databaseUrl, "username", "password");
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }
}