[fw-general] Get the database adapter without Zend_Db_Table

[BB]

Hello,

how can I get the database adapter instance in the model (or anywhere
else) without the Zend_Db_Table's getDefaultAdapter()?

Foo.php:
class Model_Foo
{
  protected $_db;
  public function __construct()
  {
    $this->_db = ???;
  }
}

in the application.ini I have the following lines:
resources.db.adapter = "mysqli"
resources.db.params.host = "localhost"
resources.db.params.username = "foo"
resources.db.params.password = "bar"
resources.db.params.dbname = "baz"