code: public function getAllMetadata()
      {
          // FIXXME Should this be implemented here or in the driver (chain)?
          $metadata = array();
          foreach ($this->driver->getAllClassNames() as $className) {
              $metadata[] = $this->getMetadataFor($className);
          }
  
          $this->validate($metadata);
  
          return $metadata;
      }
docs: Forces the factory to load the metadata of all classes known to the underlying
  mapping driver.
  
  @return array The ClassMetadata instances of all mapped classes.