django/core/serializers/json.py

"""
Serialize data to/from JSON
"""

# Avoid shadowing the standard library json module
from __future__ import absolute_import
from __future__ import unicode_literals

import datetime
import decimal
import json
import sys

from django.core.serializers.base import DeserializationError
from django.core.serializers.python import Serializer as PythonSerializer
from django.core.serializers.python import Deserializer as PythonDeserializer
from django.utils import six
from django.utils.timezone import is_aware


class Serializer(PythonSerializer):
    """
    Convert a queryset to JSON.
    """
    internal_use_only = False

    def start_serialization(self):
        if json.__version__.split('.') >= ['2', '1', '3']:
            # Use JS strings to represent Python Decimal instances (ticket #16850)
            self.options.update({'use_decimal': False})
        self._current = None
        self.json_kwargs = self.options.copy()
        self.json_kwargs.pop('stream', None)
        self.json_kwargs.pop('fields', None)
        if self.options.get('indent'):
            # Prevent trailing spaces
            self.json_kwargs['separators'] = (',', ': ')
        self.stream.write("[")

    def end_serialization(self):
        if self.options.get("indent"):
            self.stream.write("\n")
        self.stream.write("]")
        if self.options.get("indent"):
            self.stream.write("\n")

    def end_object(self, obj):
        # self._current has the field data
        indent = self.options.get("indent")
        if not self.first:
            self.stream.write(",")
            if not indent:
                self.stream.write(" ")
        if indent:
            self.stream.write("\n")
        json.dump(self.get_dump_object(obj), self.stream,
                  cls=DjangoJSONEncoder, **self.json_kwargs)
        self._current = None

    def getvalue(self):
        # Grand-parent super
        return super(PythonSerializer, self).getvalue()


def Deserializer(stream_or_string, **options):
    """
    Deserialize a stream or string of JSON data.
    """
    if not isinstance(stream_or_string, (bytes, six.string_types)):
        stream_or_string = stream_or_string.read()
    if isinstance(stream_or_string, bytes):
        stream_or_string = stream_or_string.decode('utf-8')
    try:
        objects = json.loads(stream_or_string)
        for obj in PythonDeserializer(objects, **options):
            yield obj
    except GeneratorExit:
        raise
    except Exception as e:
        # Map to deserializer error
        six.reraise(DeserializationError, DeserializationError(e), sys.exc_info()[2])


class DjangoJSONEncoder(json.JSONEncoder):
    """
    JSONEncoder subclass that knows how to encode date/time and decimal types.
    """
    def default(self, o):
        # See "Date Time String Format" in the ECMA-262 specification.
        if isinstance(o, datetime.datetime):
            r = o.isoformat()
            if o.microsecond:
                r = r[:23] + r[26:]
            if r.endswith('+00:00'):
                r = r[:-6] + 'Z'
            return r
        elif isinstance(o, datetime.date):
            return o.isoformat()
        elif isinstance(o, datetime.time):
            if is_aware(o):
                raise ValueError("JSON can't represent timezone-aware times.")
            r = o.isoformat()
            if o.microsecond:
                r = r[:12]
            return r
        elif isinstance(o, decimal.Decimal):
            return str(o)
        else:
            return super(DjangoJSONEncoder, self).default(o)

# Older, deprecated class name (for backwards compatibility purposes).
DateTimeAwareJSONEncoder = DjangoJSONEncoder