possible solution: Multiple DB connections with a service locator

AbstractAdapterServiceFactory.php

namespace Zend\Db\Adapter;

use Zend\Db\Adapter\Exception\InvalidArgumentException;

use Zend\ServiceManager\FactoryInterface;
use Zend\ServiceManager\ServiceLocatorInterface;

/**
 * @category   Zend
 * @package    Zend_Db
 * @subpackage Adapter
 */
abstract class AbstractAdapterServiceFactory implements FactoryInterface
{
    /**
     * Create db adapter service
     *
     * @param ServiceLocatorInterface $serviceLocator
     * @return Adapter
     */
    public function createService(ServiceLocatorInterface $serviceLocator)
    {
        $config = $serviceLocator->get('Config');

        $dbConfigKey = $this->getDbConfigKey();
        
        if ( false === isset($config['db'][$dbConfigKey]) ) {
            throw new \RuntimeException(sprintf("database config with key '%s' is not found", $dbConfigKey) );
        }

        return $this->factory($config['db'][$dbConfigKey],$serviceLocator);
    }
    
    /**
     * 
     * @return string
     */
    protected function getDbConfigKey()
    {
        return "default";
    }
    
    protected function factory($config,ServiceLocatorInterface $serviceLocator)
    {
        $driver               = null;
        $platform             = null;
        $queryResultPrototype = null;

        if ( isset($config['driver']) ) {
            if ( is_array($config['driver']) ) {
                $driver = $config['driver'];
            } elseif ( is_string($config['driver']) ) {
                if( class_exists($config['driver']) ) {
                    $driver = new $config['driver']();
                } else {
                    $driver = $serviceLocator->get($config['driver']);
                }
                
                if ( !is_object($platform) ) {
                    throw new InvalidArgumentException("database config['driver'] string is not a confirmed class/service name");
                }
            } else {
                throw new InvalidArgumentException("database config['driver'] must be a array or string of class/service name");
            }
        }

        if ( isset($config['platform']) ) {
            if( class_exists($config['platform']) ) {
                $platform = new $config['platform']();
            } else {
                $platform = $serviceLocator->get($config['platform']);
            }
        }

        if ( !is_object($platform) ) {
            $platform = null;
        }


        if ( isset($config['queryResultPrototype']) ) {
            if( class_exists($config['queryResultPrototype']) ) {
                $queryResultPrototype = new $config['queryResultPrototype']();
            } else {
                $queryResultPrototype = $serviceLocator->get($config['queryResultPrototype']);
            }
        }

        if ( !is_object($queryResultPrototype) ) {
            $queryResultPrototype = null;
        }

        return new Adapter($driver,$platform,$queryResultPrototype);
    }
}

BarAdapter.php

class BarAdapter extends AbstractAdapterServiceFactory
{
    /**
     *
     * @return string
     */
    protected function getDbConfigKey()
    {
        return 'bar';
    }
}

FooAdapter.php

class FooAdapter extends AbstractAdapterServiceFactory
{
    /**
     *
     * @return string
     */
    protected function getDbConfigKey()
    {
        return 'foo';
    }
}