Serialization

Serialization can be one of the most contentious areas of an API. Everyone has their own requirements, their own preferred output format & the desire to have control over what is returned.

As a result, Tastypie ships with a serializer that tries to meet the basic needs of most use cases, and the flexibility to go outside of that when you need to.

The default Serializer supports the following formats:

  • json
  • jsonp
  • xml
  • yaml
  • html

Usage

Using this class is simple. It is the default option on all Resource classes unless otherwise specified. The following code is a no-op, but demonstrate how you could use your own serializer:

from django.contrib.auth.models import User
from tastypie.resources import ModelResource
from tastypie.serializers import Serializer


class UserResource(ModelResource):
    class Meta:
        queryset = User.objects.all()
        resource_name = 'auth/user'
        excludes = ['email', 'password', 'is_superuser']
        # Add it here.
        serializer = Serializer()

Implementing Your Own Serializer

There are several different use cases here. We’ll cover simple examples of wanting a tweaked format & adding a different format.

To tweak a format, simply override it’s to_<format> & from_<format> methods. So adding the server time to all output might look like so:

import time
from tastypie.serializers import Serializer


class CustomJSONSerializer(Serializer):
    def to_json(self, data, options=None):
        options = options or {}

        data = self.to_simple(data, options)

        # Add in the current time.
        data['requested_time'] = time.time()

        return simplejson.dumps(data, cls=json.DjangoJSONEncoder, sort_keys=True)

    def from_json(self, content):
        data = simplejson.loads(content)

        if 'requested_time' in data:
            # Log the request here...
            pass

        return data

In the case of adding a different format, let’s say you want to add a CSV output option to the existing set. Your Serializer subclass might look like:

import csv
import StringIO
from tastypie.serializers import Serializer


class CSVSerializer(Serializer):
    formats = ['json', 'jsonp', 'xml', 'yaml', 'html', 'csv']
    content_types = {
        'json': 'application/json',
        'jsonp': 'text/javascript',
        'xml': 'application/xml',
        'yaml': 'text/yaml',
        'html': 'text/html',
        'csv': 'text/csv',
    }

    def to_csv(self, data, options=None):
        options = options or {}
        data = self.to_simple(data, options)
        raw_data = StringIO.StringIO()
        # Untested, so this might not work exactly right.
        for item in data:
            writer = csv.DictWriter(raw_data, item.keys(), extrasaction='ignore')
            writer.write(item)
        return raw_data

    def from_csv(self, content):
        raw_data = StringIO.StringIO(content)
        data = []
        # Untested, so this might not work exactly right.
        for item in csv.DictReader(raw_data):
            data.append(item)
        return data

Serializer Methods

A swappable class for serialization.

This handles most types of data as well as the following output formats:

* json
* jsonp
* xml
* yaml
* html

It was designed to make changing behavior easy, either by overridding the various format methods (i.e. to_json), by changing the formats/content_types options or by altering the other hook methods.

get_mime_for_format

Serializer.get_mime_for_format(self, format):

Given a format, attempts to determine the correct MIME type.

If not available on the current Serializer, returns application/json by default.

format_datetime

Serializer.format_datetime(data):

A hook to control how datetimes are formatted.

Can be overridden at the Serializer level (datetime_formatting) or globally (via settings.TASTYPIE_DATETIME_FORMATTING).

Default is iso-8601, which looks like “2010-12-16T03:02:14”.

format_date

Serializer.format_date(data):

A hook to control how dates are formatted.

Can be overridden at the Serializer level (datetime_formatting) or globally (via settings.TASTYPIE_DATETIME_FORMATTING).

Default is iso-8601, which looks like “2010-12-16”.

format_time

Serializer.format_time(data):

A hook to control how times are formatted.

Can be overridden at the Serializer level (datetime_formatting) or globally (via settings.TASTYPIE_DATETIME_FORMATTING).

Default is iso-8601, which looks like “03:02:14”.

serialize

Serializer.serialize(self, bundle, format='application/json', options={}):

Given some data and a format, calls the correct method to serialize the data and returns the result.

deserialize

Serializer.deserialize(self, content, format='application/json'):

Given some data and a format, calls the correct method to deserialize the data and returns the result.

to_simple

Serializer.to_simple(self, data, options):

For a piece of data, attempts to recognize it and provide a simplified form of something complex.

This brings complex Python data structures down to native types of the serialization format(s).

to_etree

Serializer.to_etree(self, data, options=None, name=None, depth=0):

Given some data, converts that data to an etree.Element suitable for use in the XML output.

from_etree

Serializer.from_etree(self, data):

Not the smartest deserializer on the planet. At the request level, it first tries to output the deserialized subelement called “object” or “objects” and falls back to deserializing based on hinted types in the XML element attribute “type”.

to_json

Serializer.to_json(self, data, options=None):

Given some Python data, produces JSON output.

from_json

Serializer.from_json(self, content):

Given some JSON data, returns a Python dictionary of the decoded data.

to_jsonp

Serializer.to_jsonp(self, data, options=None):

Given some Python data, produces JSON output wrapped in the provided callback.

to_xml

Serializer.to_xml(self, data, options=None):

Given some Python data, produces XML output.

from_xml

Serializer.from_xml(self, content):

Given some XML data, returns a Python dictionary of the decoded data.

to_yaml

Serializer.to_yaml(self, data, options=None):

Given some Python data, produces YAML output.

from_yaml

Serializer.from_yaml(self, content):

Given some YAML data, returns a Python dictionary of the decoded data.

to_html

Serializer.to_html(self, data, options=None):

Reserved for future usage.

The desire is to provide HTML output of a resource, making an API available to a browser. This is on the TODO list but not currently implemented.

from_html

Serializer.from_html(self, content):

Reserved for future usage.

The desire is to handle form-based (maybe Javascript?) input, making an API available to a browser. This is on the TODO list but not currently implemented.

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