Log4j2 XML define JDBC Appender and pass property

i have a maven project runnable with SpringBoot. I defined a JDBC appender and would like to pass jdbc properties from log4j2.xml

Reading Getting properties programmatically from Log4j2 XML config i did:

PUT log4j2.xml and logsCommons.properties in src/main/resources folder

In log4j2.xml

<Configuration status="warn" monitorInterval="30">
 <Properties>
   <Property name="baseDir">${bundle:logsCommons:baseDir}/</Property>
   </Properties>
   <Appenders>
     <JDBC name="jdbcAppender" tableName="event_log">
       <ConnectionFactory class="Log4j2CustomConnectionFactory"
        method="getDatabaseConnection"/> 
       <Column name="dt_event" isEventTimestamp="true" />
       ....
     </JDBC>              
   </Appenders>
   <Loggers>
   </Loggers>
</Configuration>

Use below java code:

import java.sql.Connection;
import java.sql.SQLException;
import javax.sql.DataSource;
import org.apache.commons.dbcp2.ConnectionFactory;
import org.apache.commons.dbcp2.DriverManagerConnectionFactory;
import org.apache.commons.dbcp2.PoolableConnection;
import org.apache.commons.dbcp2.PoolableConnectionFactory;
import org.apache.commons.dbcp2.PoolingDataSource;
import org.apache.commons.pool2.ObjectPool;
import org.apache.commons.pool2.impl.GenericObjectPool;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.core.LoggerContext;
import org.apache.logging.log4j.core.config.Configuration;


public class Log4j2CustomConnectionFactory{

private static interface Singleton {
    final Log4j2CustomConnectionFactoryINSTANCE = new Log4j2CustomConnectionFactory();
}

private DataSource dataSource;

private Log4j2CustomConnectionFactory() {

    LoggerContext context = (LoggerContext) LogManager.getContext(false);
    Configuration configuration = context.getConfiguration();

    String baseDirVar = configuration.getStrSubstitutor().getVariableResolver().lookup("baseDir");

    /* HERE baseDirVar IS NULL */
    /* also configuration.getStrSubstitutor().getVariableResolver().lookup("java"); return NULL */



}

public static Connection getDatabaseConnection() throws SQLException {
    return Singleton.INSTANCE.dataSource.getConnection();
}

/*..initializing Datasource with properties retrieved from Log4j2.xml.*/

}