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 XML views

This modules defines several basic views for serializing

data to XML. Submodels that have already been serialized

as XML may have their string values marked with `__is_xml__

= 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 collections as col

import copy

import xml.etree.ElementTree as ET

import six

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

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class KeyValueView(object):

"""A Key-Value XML View

This view performs advanced serialization of a data model

into XML. It first deserializes any values marked as XML so

that they can be properly reserialized later. It then follows

the following rules to perform serialization:

key : text/xml

The tag name is the key name, and the contents are the text or xml

key : Sequence

A wrapper tag is created with the key name, and each item is placed

in an 'item' tag

key : Mapping

A wrapper tag is created with the key name, and the serialize is called

on each key-value pair (such that each key gets its own tag)

:param str wrapper_name: the name of the top-level element

"""

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    def __init__(self, wrapper_name="model"):

        self.wrapper_name = wrapper_name

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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_xml__', False):

                cpy[key] = ET.fromstring(valstr)

        def serialize(rootmodel, rootkeyname):

            res = ET.Element(rootkeyname)

            if isinstance(rootmodel, col.Mapping):

                for key in rootmodel:

                    res.append(serialize(rootmodel[key], key))

            elif (isinstance(rootmodel, col.Sequence)

                    and not isinstance(rootmodel, six.string_types)):

                for val in rootmodel:

                    res.append(serialize(val, 'item'))

            elif ET.iselement(rootmodel):

                res.append(rootmodel)

            else:

                res.text = str(rootmodel)

            return res

        res = utils.StringWithAttrs(ET.tostring(serialize(cpy,

                                                          self.wrapper_name)))

        res.__is_xml__ = True

        return res

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        def serialize(rootmodel, rootkeyname):

            res = ET.Element(rootkeyname)

            if isinstance(rootmodel, col.Mapping):

                for key in rootmodel:

                    res.append(serialize(rootmodel[key], key))

            elif (isinstance(rootmodel, col.Sequence)

                    and not isinstance(rootmodel, six.string_types)):

                for val in rootmodel:

                    res.append(serialize(val, 'item'))

            elif ET.iselement(rootmodel):

                res.append(rootmodel)

            else:

                res.text = str(rootmodel)

            return res

        res = utils.StringWithAttrs(ET.tostring(serialize(cpy,

                                                          self.wrapper_name)))

        res.__is_xml__ = True

        return res