django1/django/core/serializers/json.py

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

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

import datetime
import decimal
import json
from io import BytesIO

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.encoding import smart_str
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)
        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):
        # overwrite PythonSerializer.getvalue() with base Serializer.getvalue()
        if callable(getattr(self.stream, 'getvalue', None)):
            return self.stream.getvalue()


def Deserializer(stream_or_string, **options):
    """
    Deserialize a stream or string of JSON data.
    """
    if isinstance(stream_or_string, bytes):
        stream = BytesIO(stream_or_string)
    elif isinstance(stream_or_string, unicode):
        stream = BytesIO(smart_str(stream_or_string))
    else:
        stream = stream_or_string
    try:
        for obj in PythonDeserializer(json.load(stream), **options):
            yield obj
    except GeneratorExit:
        raise
    except Exception as e:
        # Map to deserializer error
        raise DeserializationError(e)


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