Spring Transactions: Interface v Class

I am trying to use Spring Transactions, and failing. When I set them up so that my web app will launch under Tomcat, calling

TransactionAspectSupport.currentTransactionStatus ().setRollbackOnly ();

when I need to roll back a transaction, but the previous DB changes are not rolled back I have

public interface TransactServiceDAO

and

public class TransactServiceDAOImpl implements TransactServiceDAO

in my application-context-config.xml I have

<bean id = "transactService" class = "edu.mayo.bsi.backslapper.model.dao.impl.TransactServiceDAOImpl"/>

<!-- enable the configuration of transactional behavior based on annotations -->
<!-- the transactional advice (what 'happens'; see the <aop:advisor/> bean below) -->
<tx:advice id = "txAdvice" transaction-manager = "txManager">
    <!-- the transactional semantics... -->
    <tx:attributes>
        <!-- all methods starting with 'get' are read-only -->
        <tx:method name = "get*" read-only = "true"/>
        <!-- other methods use the default transaction settings (see below) -->
        <tx:method name = "*"/>
    </tx:attributes>
</tx:advice>

<!-- ensure that the above transactional advice runs for any execution of an operation defined by the TransactServiceDAO interface -->
<aop:config>
    <aop:pointcut id = "transactServiceOperation" expression = "execution(* edu.mayo.bsi.backslapper.model.dao.TransactServiceDAO.*(..))"/>
    <aop:advisor advice-ref = "txAdvice" pointcut-ref = "transactServiceOperation"/>
</aop:config>

<bean id = "txManager" class = "org.springframework.jdbc.datasource.DataSourceTransactionManager">
    <property name = "dataSource" ref = "backDataSource"/>
</bean>

<tx:advice id = "txAdvice" transaction-manager = "txManager">
    <tx:attributes>
        <tx:method name = "*" rollback-for = "Throwable"/>
        <tx:method name = "*" rollback-for = "java.sql.SQLException"/>
    </tx:attributes>
</tx:advice>

Here's an example, a routine where a (count == 0) rollback does not undo the "delete old users".

What am I doing wrong?

public String setUsers (DataSource dataSource, User theUser, String store, AdminUser[] newUsers)
{
    NamedParameterJdbcTemplate  namedParameterJdbcTemplate = new NamedParameterJdbcTemplate (dataSource);
    Map<String, Object>         params = new HashMap<String, Object> ();

    params.put ("lanID", theUser.getLanID ());
    params.put ("storeName", store);

    int count = namedParameterJdbcTemplate.update (kDeleteOldUsers, params);

    for (AdminUser curUser : newUsers)
    {
        int userID = updateUser (namedParameterJdbcTemplate, curUser.getLanID (), curUser.getFullName (), curUser.getEmail (), null);

        if (userID == kError)
            userID = addUser (namedParameterJdbcTemplate, curUser);

        params.put ("userID", Integer.valueOf (userID));
        count = namedParameterJdbcTemplate.update (kAddStoreUser, params);
        if (count == 0) // Wasn't inserted
            TransactionAspectSupport.currentTransactionStatus ().setRollbackOnly ();

        params.put ("backslapsToGive", Integer.valueOf (curUser.getBackslapsToGive ()));
        params.put ("monthlyBackslaps", Integer.valueOf (curUser.getMaxBackslaps ()));
        count = namedParameterJdbcTemplate.update (kUpdateUserStores, params);
        if (count == 0) // Wasn't updated
            TransactionAspectSupport.currentTransactionStatus ().setRollbackOnly ();
    }

    return null;
}

Thank you, Greg