OpenStack Study: generic.py

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# Copyright 2013 Red Hat, Inc.

#

# Licensed under the Apache License, Version 2.0 (the "License"); you may

# not use this file except in compliance with the License. You may obtain

# a copy of the License at

#

# http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT

# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the

# License for the specific language governing permissions and limitations

# under the License.

"""Provides generic JSON views

This modules defines several basic views for serializing

data to JSON. Submodels that have already been serialized

as JSON may have their string values marked with `__is_json__

= True` using :class:`openstack.common.report.utils.StringWithAttrs`

(each of the classes within this module does this automatically,

and non-naive serializers check for this attribute and handle

such strings specially)

"""

import copy

from nova.openstack.common import jsonutils as json

import nova.openstack.common.report.utils as utils

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class BasicKeyValueView(object):

"""A Basic Key-Value JSON View

This view performs a naive serialization of a model

into JSON by simply calling :func:`json.dumps` on the model

"""

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    def __call__(self, model):

        res = utils.StringWithAttrs(json.dumps(model.data))

        res.__is_json__ = True

        return res

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class KeyValueView(object):

"""A Key-Value JSON View

This view performs advanced serialization to a model

into JSON. It does so by first checking all values to

see if they are marked as JSON. If so, they are deserialized

using :func:`json.loads`. Then, the copy of the model with all

JSON deserialized is reserialized into proper nested JSON using

:func:`json.dumps`.

"""

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    def __call__(self, model):

        # this part deals with subviews that were already serialized

        cpy = copy.deepcopy(model)

        for key, valstr in model.items():

            if getattr(valstr, '__is_json__', False):

                cpy[key] = json.loads(valstr)

        res = utils.StringWithAttrs(json.dumps(cpy.data))

        res.__is_json__ = True

        return res