log4j2 Il gestore JDBC non può connettersi al database

Ok la soluzione è:

1- crea una classe Connection Factory

import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;

import javax.sql.DataSource;

import org.apache.commons.dbcp.DriverManagerConnectionFactory;
import org.apache.commons.dbcp.PoolableConnection;
import org.apache.commons.dbcp.PoolableConnectionFactory;
import org.apache.commons.dbcp.PoolingDataSource;
import org.apache.commons.pool.impl.GenericObjectPool;


public class ConnectionFactory {

    private static interface Singleton {
        final ConnectionFactory INSTANCE = new ConnectionFactory();
    }

    private final DataSource dataSource;

    private ConnectionFactory() {

        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
            System.exit(0);
        }

        Properties properties = new Properties();
        properties.setProperty("user", "root");
        properties.setProperty("password", "root");

        GenericObjectPool<PoolableConnection> pool = new GenericObjectPool<PoolableConnection>();
        DriverManagerConnectionFactory connectionFactory = new DriverManagerConnectionFactory(
                "jdbc:mysql://example.org:3306/exampleDb", properties
        );
        new PoolableConnectionFactory(connectionFactory, pool, null, "SELECT 1", 3, false, false, Connection.TRANSACTION_READ_COMMITTED);
        this.dataSource = new PoolingDataSource(pool);
    }

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

2- crea un file di configurazione in src/main/resources chiamato log4j2.xml

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="TRACE" monitorInterval="30">
    <Appenders>
        <Console name="Console" target="SYSTEM_OUT">
            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" />
        </Console>
        <JDBC name="databaseAppender" tableName="logs">
            <ConnectionFactory class="my.pack.ConnectionFactory"
                method="getDatabaseConnection" />
            <!-- <Column name="id" literal="LOGGING.APPLICATION_LOG_SEQUENCE.NEXTVAL" /> -->
            <Column name="date" isEventTimestamp="true" />
            <Column name="level" pattern="%level" />
            <Column name="message" pattern="%message" />
            <Column name="class" pattern="%class" /> 
        </JDBC>
    </Appenders>
    <Loggers>
        <Root level="trace">
            <AppenderRef ref="Console" />
            <AppenderRef ref="databaseAppender" />
        </Root>
    </Loggers>
</Configuration>

3- crea una tabella come questa:

4- aggiungi il connettore mysql a {tomcat}/bin

Maven suggerisce:

    <commons-dbcp.version>1.4</commons-dbcp.version>

    <commons-pool.version>1.6</commons-pool.version>

    <dependency>
        <groupId>commons-dbcp</groupId>
        <artifactId>commons-dbcp</artifactId>
        <version>${commons-dbcp.version}</version>
    </dependency>

    <dependency>
        <groupId>commons-pool</groupId>
        <artifactId>commons-pool</artifactId>
        <version>${commons-pool.version}</version>
    </dependency>