abstract class BaseBO<Id, Entity, DAOClass extends DAO<Id, Entity>> implements BO<Id, Entity, DAOClass> {
    DAOClass dao;

    public DAOClass getDAO() {
        return dao;
    }
    //...
}

public class TaskBO extends BaseBO<Long, Task, TaskDAO> implements BO<Long, Task, TaskDAO> {
    //пусто   
}

<bean id="TaskBO" class="com.otv.model.bo.TaskBO">
        <property name="DAO" ref="TaskDAO" />
</bean>

<bean id="TaskDAO" class="com.otv.model.dao.TaskDAO">
        <property name="sessionFactory" ref="SessionFactory" />
    </bean>

@ManagedProperty(value="#{TaskBO}")
TaskBO taskBO;

@ManagedProperty(value="#{TaskBO}")
BO<Long, Task, TaskDAO,> taskBO;