_google_appengine_ext_db.py 文件源码

def encode_xdb_key(key, encoder=None):
    """
    Convert the `db.Key` to it's entity and encode it.
    """
    gae_objects = getGAEObjects(encoder.context.extra)

    klass = db.class_for_kind(key.kind())

    try:
        referenced_object = gae_objects.get(klass, key)
    except KeyError:
        referenced_object = db.get(key)
        gae_objects.set(klass, key, referenced_object)

    if not referenced_object:
        encoder.writeElement(None)
    else:
        encoder.writeObject(referenced_object)