<beans>
    <!--BAD: A non-abstract bean should use a concrete class.
        'ConnectionPool' is an abstract class.-->
    <bean id="wrongConnectionPool" 
            class="documentation.examples.spring.ConnectionPool"/>
    <bean id="appReqPool1" class="documentation.examples.spring.AppRequestConnectionPool" 
            parent="wrongConnectionPool"/>

    <!--GOOD: A bean that specifies an abstract class should be declared 'abstract'.-->
    <bean id="connectionPool" 
            class="documentation.examples.spring.ConnectionPool" abstract="true"/>
    <bean id="appReqPool2" class="documentation.examples.spring.AppRequestConnectionPool" 
            parent="connectionPool"/>
</beans>