/usr/lib/python3/dist-packages/josepy/interfaces.py is in python3-josepy 1.1.0-1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 | """JOSE interfaces."""
import abc
import collections
import json
import six
from josepy import errors, util
# pylint: disable=no-self-argument,no-method-argument,no-init,inherit-non-class
# pylint: disable=too-few-public-methods
@six.add_metaclass(abc.ABCMeta)
class JSONDeSerializable(object):
# pylint: disable=too-few-public-methods
"""Interface for (de)serializable JSON objects.
Please recall, that standard Python library implements
:class:`json.JSONEncoder` and :class:`json.JSONDecoder` that perform
translations based on respective :ref:`conversion tables
<conversion-table>` that look pretty much like the one below (for
complete tables see relevant Python documentation):
.. _conversion-table:
====== ======
JSON Python
====== ======
object dict
... ...
====== ======
While the above **conversion table** is about translation of JSON
documents to/from the basic Python types only,
:class:`JSONDeSerializable` introduces the following two concepts:
serialization
Turning an arbitrary Python object into Python object that can
be encoded into a JSON document. **Full serialization** produces
a Python object composed of only basic types as required by the
:ref:`conversion table <conversion-table>`. **Partial
serialization** (accomplished by :meth:`to_partial_json`)
produces a Python object that might also be built from other
:class:`JSONDeSerializable` objects.
deserialization
Turning a decoded Python object (necessarily one of the basic
types as required by the :ref:`conversion table
<conversion-table>`) into an arbitrary Python object.
Serialization produces **serialized object** ("partially serialized
object" or "fully serialized object" for partial and full
serialization respectively) and deserialization produces
**deserialized object**, both usually denoted in the source code as
``jobj``.
Wording in the official Python documentation might be confusing
after reading the above, but in the light of those definitions, one
can view :meth:`json.JSONDecoder.decode` as decoder and
deserializer of basic types, :meth:`json.JSONEncoder.default` as
serializer of basic types, :meth:`json.JSONEncoder.encode` as
serializer and encoder of basic types.
One could extend :mod:`json` to support arbitrary object
(de)serialization either by:
- overriding :meth:`json.JSONDecoder.decode` and
:meth:`json.JSONEncoder.default` in subclasses
- or passing ``object_hook`` argument (or ``object_hook_pairs``)
to :func:`json.load`/:func:`json.loads` or ``default`` argument
for :func:`json.dump`/:func:`json.dumps`.
Interestingly, ``default`` is required to perform only partial
serialization, as :func:`json.dumps` applies ``default``
recursively. This is the idea behind making :meth:`to_partial_json`
produce only partial serialization, while providing custom
:meth:`json_dumps` that dumps with ``default`` set to
:meth:`json_dump_default`.
To make further documentation a bit more concrete, please, consider
the following imaginatory implementation example::
class Foo(JSONDeSerializable):
def to_partial_json(self):
return 'foo'
@classmethod
def from_json(cls, jobj):
return Foo()
class Bar(JSONDeSerializable):
def to_partial_json(self):
return [Foo(), Foo()]
@classmethod
def from_json(cls, jobj):
return Bar()
"""
@abc.abstractmethod
def to_partial_json(self): # pragma: no cover
"""Partially serialize.
Following the example, **partial serialization** means the following::
assert isinstance(Bar().to_partial_json()[0], Foo)
assert isinstance(Bar().to_partial_json()[1], Foo)
# in particular...
assert Bar().to_partial_json() != ['foo', 'foo']
:raises josepy.errors.SerializationError:
in case of any serialization error.
:returns: Partially serializable object.
"""
raise NotImplementedError()
def to_json(self):
"""Fully serialize.
Again, following the example from before, **full serialization**
means the following::
assert Bar().to_json() == ['foo', 'foo']
:raises josepy.errors.SerializationError:
in case of any serialization error.
:returns: Fully serialized object.
"""
def _serialize(obj):
if isinstance(obj, JSONDeSerializable):
return _serialize(obj.to_partial_json())
if isinstance(obj, six.string_types): # strings are Sequence
return obj
elif isinstance(obj, list):
return [_serialize(subobj) for subobj in obj]
elif isinstance(obj, collections.Sequence):
# default to tuple, otherwise Mapping could get
# unhashable list
return tuple(_serialize(subobj) for subobj in obj)
elif isinstance(obj, collections.Mapping):
return dict((_serialize(key), _serialize(value))
for key, value in six.iteritems(obj))
else:
return obj
return _serialize(self)
@util.abstractclassmethod
def from_json(cls, jobj): # pylint: disable=unused-argument
"""Deserialize a decoded JSON document.
:param jobj: Python object, composed of only other basic data
types, as decoded from JSON document. Not necessarily
:class:`dict` (as decoded from "JSON object" document).
:raises josepy.errors.DeserializationError:
if decoding was unsuccessful, e.g. in case of unparseable
X509 certificate, or wrong padding in JOSE base64 encoded
string, etc.
"""
# TypeError: Can't instantiate abstract class <cls> with
# abstract methods from_json, to_partial_json
return cls() # pylint: disable=abstract-class-instantiated
@classmethod
def json_loads(cls, json_string):
"""Deserialize from JSON document string."""
try:
loads = json.loads(json_string)
except ValueError as error:
raise errors.DeserializationError(error)
return cls.from_json(loads)
def json_dumps(self, **kwargs):
"""Dump to JSON string using proper serializer.
:returns: JSON document string.
:rtype: str
"""
return json.dumps(self, default=self.json_dump_default, **kwargs)
def json_dumps_pretty(self):
"""Dump the object to pretty JSON document string.
:rtype: str
"""
return self.json_dumps(sort_keys=True, indent=4, separators=(',', ': '))
@classmethod
def json_dump_default(cls, python_object):
"""Serialize Python object.
This function is meant to be passed as ``default`` to
:func:`json.dump` or :func:`json.dumps`. They call
``default(python_object)`` only for non-basic Python types, so
this function necessarily raises :class:`TypeError` if
``python_object`` is not an instance of
:class:`IJSONSerializable`.
Please read the class docstring for more information.
"""
if isinstance(python_object, JSONDeSerializable):
return python_object.to_partial_json()
else: # this branch is necessary, cannot just "return"
raise TypeError(repr(python_object) + ' is not JSON serializable')
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