django-loadjson 0.1.2

Loadjson management command for Django

Django management command to load json data of any shape by defining “manifest” that describes mapping instructions.

Requirements

Python 2.7, 3.4, 3.5 Django >= 1.7

Installation

pip install django-loadjson

Quick setup

Include loadjson in settings.py

INSTALLED_APPS = [
    ... ,
    'loadjson',
    ...
]

Define loadjson data directories - a place loadjson will look for data (.json) files.

LOAD_JSON = {
    'DATA_DIRS': [os.path.join(BASE_DIR, 'dumpdata')],
}

Dump all your .json files inside the specified directory(ies).

Each *.json file must also have corresponding *.manifest.json that describes how the data should be handled. For “manifest” reference, see Manifest section.

Once the data and manifest is in place, run

python manage.py loadjson <data_name>, where <data_name> corresponds to the filename of the data (with or without the .json part).

Note, loadjson will look in all specified directories for the requested <data_name> and will use the first file it will find. Same goes for the manifest file. Data file and manifest do not have to live in the same directory, but both must be in a path of defined “DATA_DIRS”.

It is also possible to handle data and manifest in other ways by providing custom “finder_classes”. See Advanced Usage for instructions.

Manifest

• model (required) - a string in format “.”

• mapping (required) - an object representing the model - data mapping.

• parsers (optional) - an object the describes how to parse the data. Supported types:

  • string - convert to string

  • integer - convert to integer

  • boolean - convert to boolean. Optional, define "invert": true to invert.

  • datetime - parse datetime string

  • relative_key - lookup the relative key by the field value in another dataset. Required:

    • data_name - is a data name where related object should be looked up.

    • rk_lookup - the field for the lookup in the related dataset using one key. Ex., “email”.

    • lookup - overwrite the related data lookup field(s). By default will use the lookup fields that are defined in data manifest.

    • many (optional) - for many-to-many relationship.

  • relative_object - get/create/update a related object. data_name or manifest required

    • data_name - for regular manifest lookup

    • manifest - define manifest right on the spot

    • many - one related object or many-to-many relationship.

• lookup (required for updates are relative lookups) - a string or a list of fields to use when looking up an object. Ex., id, email, ["username", "email"]. Note, lookup fields are used to lookup an object. The result of a lookup must be one object, so choose accordingly.

• nullable (optional) - a list of fields that are nullable.

• m2m_fields (optional) - a list of many-to-many fields. Note, if data contains many-to-many field, this field should include it, or alternatively use custom adaptors to handle it, otherwise Django will throw an error when saving.

Example:

users.json

[
    {
        "username": "PinkRabbit",
        "email": "[e-mail]"
        "member_since": "",
        "active": true,
        "not_superuser": true,
        "preferences": {
            "email_notifications: true,
            "number_of_friends": "2"
        },
        "friends": ["[e-mail]", "[e-mail]"],
        "badges": [
            {
                "name": "For being pink",
                "date_awarded": ""
            },
            {
                "name": "For being there for friends",
                "date_awarded": ""
            }
         ]
    },
    ...
]

users.manifest.json

{
    "model": "account.User",
    "lookup": "pk",
    "mapping": {
        "username": "username",
        "email": "email",
        "date_joined": "member_since",
        "active": "active",
        "is_superuser": "not_superuser",
        "email_notifications": "preferences.email_notifications",
        "friends_number": "preferences.number_of_friends",
        "friends": "friends",
        "badges": "badges"
    },
    "parsers": {
        "is_superuser: {
            "type": "boolean",
            "invert": true
        },
        "date_joined": {
            "type": "datetime"
        },
        "friends": {
            "type": "relative_key",
            "data_name": "users",
            "rk_lookup": "email",
            "lookup": "username",
            "many": true
        },
        "badges": {
            "type": "relative_object",
            "many": true,
            "manifest" {
                "model": "account.Badge"
                "mapping": {
                    "name": "name",
                    "awarded": "date_awarded"
                },
                "parsers": {
                    "awarded": {
                        "type": "datetime"
                    }
                },
                "lookup": "name"
            }
        }
    }
}

LOAD_JSON settings

All loadjson-related settings should go into LOAD_JSON var inside project’s settings.py.

Possible LOAD_JSON settings:

• DATA_DIRS (required) - a list of absolute paths to use by the default finder to find data and manifest.

• ADAPTOR_CLASSES (optional) - a list of classes that are used to customize the import. Extend loadjson.adaptors.BaseAdaptor to define your custom adaptors. Defaults to None.

• MODEL_HANDLER (optional) - a string that references a class that handles model lookups. Defaults to loadjson.adaptors.ModelHandler

• FINDER_CLASSES (optional) - a list of classes that are used to find data. By default loadjson uses loadjson.finders.DefaultDataFinder that uses defined DATA_DIRS to find data and manifest.

• MANIFEST_DEFAULTS (optional) - a dictionary of default manifest values to use.

Defining ADAPTOR_CLASSES

ADAPTOR_CLASSES are used to further massage the data before saving. To define Adaptor Class, extend loadjson.adaptors.BaseAdaptor and overwrite adapt and/or adapt_post_save methods like so:

from loadjson.adaptors import BaseAdaptor


class MyCusomAdaptor(BaseAdaptor):
    """
    Available attributes:
    - model - model class
    - app_model - a string in format <app_label>.<model_name>
    - manifest - a dictionary with defined manifest values
    """

    def adapt(self, data):
        """
        Method provides a base hook to provide additional data, set defaults,
        or modify the data before saving.

        Usage: what returned gets saved
        """
        return data

    def adapt_post_save(self, obj, data, m2m_data):
        """
        In some cases (like saving many-to-many relations) data might require
        some additional tweaks. That is done here.
        Note: Many-to-Many objects are attached by default, however in case if many-to-many relationship
        is done through a custom model, this method provides a hook to process such customization.
        """
        pass

Don’t forget to include your custom adaptors in LOAD_JSON.ADAPTOR_CLASSES.

Advanced usage

MODEL_HANDLER

Define custom ModelHandle if you want to use custom model manager, or your same method has any customization. get, create, get_or_create, update_or_create methods are available for overwrite.

FINDER_CLASSES

It is also possible to overwrite or extend the default finder classes. The purpose of the finder class is to lookup the data by data_name. DefaultDataFinder is a default finder, but can be extended by defining FINDER_CLASSES in LOAD_JSON settings. Note, if you define this setting and not include DefaultDataFinder, then it will not be used, unless you add it explicitly as well.

It is possible to define as many finders as you will, but be aware that only the first occurrence found will be used.