standalone.xml

 <subsystem xmlns="urn:jboss:domain:datasources:5.0">
            <datasources>
                <datasource jndi-name="java:jboss/datasources/ExampleDS" pool-name="ExampleDS" enabled="true" use-java-context="true" statistics-enabled="${wildfly.datasources.statistics-enabled:${wildfly.statistics-enabled:false}}">
                    <connection-url>jdbc:h2:mem:test;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=FALSE</connection-url>
                    <driver>h2</driver>
                    <security>
                        <user-name>sa</user-name>
                        <password>sa</password>
                    </security>
                </datasource>
                <datasource jndi-name="java:/jboss/datasources/KeycloakDS" pool-name="KeycloakDS" enabled="true" use-java-context="true">
                    <connection-url>jdbc:mysql://localhost:3306/keycloak?useSSL=false&amp;amp;useLegacyDatetimeCode=false&amp;amp;serverTimezone=Europe/Amsterdam&amp;amp;characterEncoding=UTF-8</connection-url>
                    <driver>mysql</driver>
                    <security>
                        <user-name>keycloak</user-name>
                        <password>keycloak</password>
                    </security>
                    <validation>
                        <valid-connection-checker class-name="org.jboss.jca.adapters.jdbc.extensions.mysql.MySQLValidConnectionChecker"/>
                        <validate-on-match>true</validate-on-match>
                        <exception-sorter class-name="org.jboss.jca.adapters.jdbc.extensions.mysql.MySQLValidConnectionChecker"/>
                    </validation>
                </datasource>
                <drivers>
                    <driver name="h2" module="com.h2database.h2">
                        <xa-datasource-class>org.h2.jdbcx.JdbcDataSource</xa-datasource-class>
                    </driver>
                    <driver name="mysql" module="org.mysql">
                        <driver-class>com.mysql.jdbc.Driver</driver-class>
                    </driver>
                </drivers>
            </datasources>
        </subsystem>