关于在Django中Json无法序列化datetime的解决办法

Posted 2020-10-09 KeepLearningEverday

　　

　　我们在网页设计时经常会在前端和后台进行交互，前端回传的方法可以时redirect一个地址加上显式的参数，第二个办法就是使用Ajax结构。那么在传到view函数中进行处理后是需要通过Json格式进行返回给前端，不然前端时不认识返回的数据，此时就需要使用到Json的序列化。

　　如果是从数据库中取的数据往往时queryset类型，Json无法直接序列化，需要先将其用list转成列表的形式再进行json，此方法可以解决大部分的问题，但是如果数据中包含datetime类型json就会报错。无法对其序列化，显示如下：

　　

　　看源码，问题出在哪里？

　　从源码中我们可以看到json只能序列化str类型的数据。那么就没别的办法了吗？

方法一　　

　　我们再来看源码：

def dumps(obj, *, skipkeys=False, ensure_ascii=True, check_circular=True,
        allow_nan=True, cls=None, indent=None, separators=None,
        default=None, sort_keys=False, **kw):
    """Serialize ``obj`` to a JSON formatted ``str``.

    If ``skipkeys`` is true then ``dict`` keys that are not basic types
    (``str``, ``int``, ``float``, ``bool``, ``None``) will be skipped
    instead of raising a ``TypeError``.

    If ``ensure_ascii`` is false, then the return value can contain non-ASCII
    characters if they appear in strings contained in ``obj``. Otherwise, all
    such characters are escaped in JSON strings.

    If ``check_circular`` is false, then the circular reference check
    for container types will be skipped and a circular reference will
    result in an ``OverflowError`` (or worse).

    If ``allow_nan`` is false, then it will be a ``ValueError`` to
    serialize out of range ``float`` values (``nan``, ``inf``, ``-inf``) in
    strict compliance of the JSON specification, instead of using the
    javascript equivalents (``NaN``, ``Infinity``, ``-Infinity``).

    If ``indent`` is a non-negative integer, then JSON array elements and
    object members will be pretty-printed with that indent level. An indent
    level of 0 will only insert newlines. ``None`` is the most compact
    representation.

    If specified, ``separators`` should be an ``(item_separator, key_separator)``
    tuple.  The default is ``(\', \', \': \')`` if *indent* is ``None`` and
    ``(\',\', \': \')`` otherwise.  To get the most compact JSON representation,
    you should specify ``(\',\', \':\')`` to eliminate whitespace.

    ``default(obj)`` is a function that should return a serializable version
    of obj or raise TypeError. The default simply raises TypeError.

    If *sort_keys* is true (default: ``False``), then the output of
    dictionaries will be sorted by key.

    To use a custom ``JSONEncoder`` subclass (e.g. one that overrides the
    ``.default()`` method to serialize additional types), specify it with
    the ``cls`` kwarg; otherwise ``JSONEncoder`` is used.

    """
    # cached encoder
    if (not skipkeys and ensure_ascii and
        check_circular and allow_nan and
        cls is None and indent is None and separators is None and
        default is None and not sort_keys and not kw):
        return _default_encoder.encode(obj)
    if cls is None:
        cls = JSONEncoder
    return cls(
        skipkeys=skipkeys, ensure_ascii=ensure_ascii,
        check_circular=check_circular, allow_nan=allow_nan, indent=indent,
        separators=separators, default=default, sort_keys=sort_keys,
        **kw).encode(obj)


_default_decoder = JSONDecoder(object_hook=None, object_pairs_hook=None)

json.dumps源码

　　其中提到了：

　　所以我们可以尝试自定义JsonEncoder：

class CJSONEncoder(self,o):
    if isinstance(o,datetime.datetime):
        return o.strftime("%Y-%m-%d %H-%M-%S")
    if isinstance(o,datetime.date):
        return o.strftime("%Y-%m-%d")
    else:reture json.JSONEncoder.default(self,o)

　　然后在Json序列化时使用 json.dumps(data,cls = CJSONEncoder)

　　

方法2：

　　如果取数据库的时候没有外键的话还可以使用django内置的方法：import django.core中的serializers，专用于序列化queryset类 data = serializers.serialize(\'json\',data) 直接可将queryset序列化，局限就在与对外键的支持不够好。