public function load($resource, $type = null)
    {
        if (null === $type) {
            $type = $this->getDefaultResourceType();
            if (empty($type)) {

                throw new Zend_Loader_Exception('No resource type specified');
            }
        }
        if (!$this->hasResourceType($type)) {

            throw new Zend_Loader_Exception('Invalid resource type specified');
        }
        $namespace = $this->_resourceTypes[$type]['namespace'];
        $class     = $namespace . '_' . ucfirst($resource);
        if (!isset($this->_resources[$class])) {
            $this->_resources[$class] = new $class;
        }
        return $this->_resources[$class];
    }