pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>java-examples</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>com.opencsv</groupId>
            <artifactId>opencsv</artifactId>
            <version>5.5.2</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.17</version>
        </dependency>
    </dependencies>

</project>

подключаемся к mysql и записываем таблицу в csv.java

import com.opencsv.CSVWriter;

import java.io.FileWriter;
import java.sql.*;


public class SqlToCsv {

    public static void main(String[] args) throws Exception {

        Class.forName("com.mysql.cj.jdbc.Driver");
        try (CSVWriter writer = new CSVWriter(new FileWriter("filename.csv"))) {
            Boolean includeHeaders = true;
            Statement statement = null;
            ResultSet myResultSet = null;
            try {
                Connection connection = DriverManager.getConnection(
                        "jdbc:mysql://db-mysql-jlkjlkghjkn.com:25560/defaultdb?allowPublicKeyRetrieval=true&useSSL=false", "admin", "admin");

                if (connection != null) {

                    statement = connection.createStatement();
                    myResultSet = statement.executeQuery("SELECT * FROM stat_online;");

                    writer.writeAll(myResultSet, includeHeaders);
                }
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
    }
}