Convert schema-described Zope 3 objects to XML and back
Project description
Schema To XML
Introduction
This package can convert objects described by Zope 3 schema to simple XML structures. It’s also able to convert this XML back into objects. The export and import processes are completely schema-driven; any attribute not described in the schema is not seen by this system at all.
This system can be used to create export and import systems for Zope 3 applications. It could also be used to provide XML representations of objects for other purposes, such as XSLT transformations, or even just to get a full-text representation for index purposes.
The package lies on lxml for the serialization to XML.
Serialization
Let’s first define a simple Zope 3 schema:
>>> from zope import interface, schema >>> class IName(interface.Interface): ... first_name = schema.TextLine(title=u'First name') ... last_name = schema.TextLine(title=u'Last name')
Let’s now make a class that implements this schema:
>>> from zope.interface import implements >>> class Name(object): ... implements(IName) ... def __init__(self, first_name, last_name): ... self.first_name = first_name ... self.last_name = last_name
Let’s make an instance of the class:
>>> name = Name('Karel', 'Titulaer')
Now let’s serialize it to XML:
>>> from z3c.schema2xml import serialize >>> print serialize('container', IName, name) <container> <first_name>Karel</first_name> <last_name>Titulaer</last_name> </container>
This also works for other kinds of fields:
>>> from zope import interface, schema >>> class IAddress(interface.Interface): ... street_name = schema.TextLine(title=u'Street name') ... number = schema.Int(title=u'House number') >>> class Address(object): ... implements(IAddress) ... def __init__(self, street_name, number): ... self.street_name = street_name ... self.number = number >>> address = Address('Hofplein', 42) >>> print serialize('container', IAddress, address) <container> <street_name>Hofplein</street_name> <number>42</number> </container>
If a field is not filled in, the serialization will result in an empty element:
>>> address2 = Address(None, None) >>> print serialize('container', IAddress, address2) <container> <street_name/> <number/> </container>
If a schema defines an Object field with its own schema, the serialization can also handle this:
>>> class IPerson(interface.Interface): ... name = schema.Object(title=u"Name", schema=IName) ... address = schema.Object(title=u"Address", schema=IAddress) >>> class Person(object): ... implements(IPerson) ... def __init__(self, name, address): ... self.name = name ... self.address = address >>> person = Person(name, address) >>> print serialize('person', IPerson, person) <person> <name> <first_name>Karel</first_name> <last_name>Titulaer</last_name> </name> <address> <street_name>Hofplein</street_name> <number>42</number> </address> </person>
A schema can also define a List field with elements with their own schema. Let’s make an object and serialize it:
>>> class ICommission(interface.Interface): ... members = schema.List( ... title=u"Commission", ... value_type=schema.Object(__name__='person', ... schema=IPerson))
Note that we have to explicitly specify __name__ for the field that’s used for value_type here, otherwise we have no name to serialize to XML with.
>>> class Commission(object): ... implements(ICommission) ... def __init__(self, members): ... self.members = members>>> commission = Commission( ... [person, Person(Name('Chriet', 'Titulaer'), Address('Ruimteweg', 3))]) >>> print serialize('commission', ICommission, commission) <commission> <members> <person> <name> <first_name>Karel</first_name> <last_name>Titulaer</last_name> </name> <address> <street_name>Hofplein</street_name> <number>42</number> </address> </person> <person> <name> <first_name>Chriet</first_name> <last_name>Titulaer</last_name> </name> <address> <street_name>Ruimteweg</street_name> <number>3</number> </address> </person> </members> </commission>
We get an adapter lookop failure whenever we try to serialize a field type for which there’s no an serializer:
>>> class IWithNonSerializableField(interface.Interface): ... field = schema.Field(title=u"Commission") >>> class NotSerializable(object): ... implements(IWithNonSerializableField) ... def __init__(self, value): ... self.field = value >>> not_serializable = NotSerializable(None) >>> serialize('noway', IWithNonSerializableField, not_serializable) Traceback (most recent call last): ... TypeError: ('Could not adapt', <zope.schema._bootstrapfields.Field object at ...>, <InterfaceClass z3c.schema2xml._schema2xml.IXMLGenerator>)
Deserialization
Now we want to deserialize XML according to a schema to an object that provides this schema.
>>> from z3c.schema2xml import deserialize >>> xml = ''' ... <container> ... <first_name>Karel</first_name> ... <last_name>Titulaer</last_name> ... </container> ... ''' >>> name = Name('', '') >>> deserialize(xml, IName, name) >>> name.first_name u'Karel' >>> name.last_name u'Titulaer'
The order of the fields in XML does not matter:
>>> xml = ''' ... <container> ... <last_name>Titulaer</last_name> ... <first_name>Karel</first_name> ... </container> ... ''' >>> name = Name('', '') >>> deserialize(xml, IName, name) >>> name.first_name u'Karel' >>> name.last_name u'Titulaer'
After deserialization, the object alsoProvides the schema interface:
>>> IName.providedBy(name) True
This also works for other kinds of fields:
>>> xml = ''' ... <container> ... <street_name>Hofplein</street_name> ... <number>42</number> ... </container> ... ''' >>> address = Address('', 0) >>> deserialize(xml, IAddress, address) >>> address.street_name u'Hofplein' >>> address.number 42
If a schema defines an Object field with its own schema, the serialization can also handle this:
>>> xml = ''' ... <person> ... <name> ... <first_name>Karel</first_name> ... <last_name>Titulaer</last_name> ... </name> ... <address> ... <street_name>Hofplein</street_name> ... <number>42</number> ... </address> ... </person> ... ''' >>> person = Person(Name('', ''), Address('', 0)) >>> deserialize(xml, IPerson, person) >>> person.name.first_name u'Karel' >>> person.name.last_name u'Titulaer' >>> person.address.street_name u'Hofplein' >>> person.address.number 42 >>> IPerson.providedBy(person) True >>> IName.providedBy(person.name) True >>> IAddress.providedBy(person.address) True
Again the order in which the fields come in XML shouldn’t matter:
>>> xml = ''' ... <person> ... <address> ... <number>42</number> ... <street_name>Hofplein</street_name> ... </address> ... <name> ... <last_name>Titulaer</last_name> ... <first_name>Karel</first_name> ... </name> ... </person> ... ''' >>> person = Person(Name('', ''), Address('', 0)) >>> deserialize(xml, IPerson, person) >>> person.name.first_name u'Karel' >>> person.name.last_name u'Titulaer' >>> person.address.street_name u'Hofplein' >>> person.address.number 42 >>> IPerson.providedBy(person) True >>> IName.providedBy(person.name) True >>> IAddress.providedBy(person.address) True >>> xml = ''' ... <commission> ... <members> ... <person> ... <name> ... <first_name>Karel</first_name> ... <last_name>Titulaer</last_name> ... </name> ... <address> ... <street_name>Hofplein</street_name> ... <number>42</number> ... </address> ... </person> ... <person> ... <name> ... <first_name>Chriet</first_name> ... <last_name>Titulaer</last_name> ... </name> ... <address> ... <street_name>Ruimteweg</street_name> ... <number>3</number> ... </address> ... </person> ... </members> ... </commission> ... ''' >>> commission = Commission([]) >>> deserialize(xml, ICommission, commission) >>> len(commission.members) 2 >>> member = commission.members[0] >>> member.name.first_name u'Karel' >>> member.address.street_name u'Hofplein' >>> member = commission.members[1] >>> member.name.first_name u'Chriet' >>> member.address.street_name u'Ruimteweg'
Whenever the XML element is empty, the resulting value should be None:
>>> from z3c.schema2xml import deserialize >>> xml = ''' ... <container> ... <first_name></first_name> ... <last_name/> ... </container> ... ''' >>> name = Name('', '') >>> deserialize(xml, IName, name) >>> name.first_name is None True >>> name.last_name is None True
For all kinds of fields, like strings and ints…:
>>> xml = ''' ... <container> ... <street_name/> ... <number/> ... </container> ... ''' >>> address = Address('', 0) >>> deserialize(xml, IAddress, address) >>> address.street_name is None True >>> address.number is None True
…and the fields of subobjects (but not the subobject themselves!):
>>> xml = ''' ... <person> ... <name> ... <first_name/> ... <last_name/> ... </name> ... <address> ... <street_name/> ... <number/> ... </address> ... </person> ... ''' >>> person = Person(Name('', ''), Address('', 0)) >>> deserialize(xml, IPerson, person) >>> person.name.first_name is None True >>> person.name.last_name is None True >>> IPerson.providedBy(person) True >>> IName.providedBy(person.name) True >>> person.address is None False >>> person.address.street_name is None True >>> person.address.number is None True >>> IAddress.providedBy(person.address) True
Similarly, where a sequence is expected the value should be an empty sequence:
>>> xml = ''' ... <commission> ... <members/> ... </commission> ... ''' >>> commission = Commission([]) >>> deserialize(xml, ICommission, commission) >>> len(commission.members) 0
TextLine, Int, Object and List have just been tested. Now follow tests for the other field types that have a serializer.
Datetime
Datetime objects:
>>> from datetime import datetime >>> class IWithDatetime(interface.Interface): ... datetime = schema.Datetime(title=u'Date and time') >>> class WithDatetime(object): ... implements(IWithDatetime) ... def __init__(self, datetime): ... self.datetime = datetime >>> with_datetime = WithDatetime(datetime(2006, 12, 31)) >>> xml = serialize('container', IWithDatetime, with_datetime) >>> print xml <container> <datetime>2006-12-31T00:00:00</datetime> </container> >>> new_datetime = WithDatetime(None) >>> deserialize(xml, IWithDatetime, new_datetime) >>> new_datetime.datetime.year 2006 >>> new_datetime.datetime.month 12 >>> new_datetime.datetime.day 31
Let’s try it with the field not filled in:
>>> with_datetime = WithDatetime(None) >>> xml = serialize('container', IWithDatetime, with_datetime) >>> print xml <container> <datetime/> </container> >>> new_datetime= WithDatetime(None) >>> deserialize(xml, IWithDatetime, new_datetime) >>> new_datetime.datetime is None True
Choice
Choice fields. For now, we only work with Choice fields that have text values:
>>> from zc.sourcefactory.basic import BasicSourceFactory >>> class ChoiceSource(BasicSourceFactory): ... def getValues(self): ... return [u'alpha', u'beta'] >>> class IWithChoice(interface.Interface): ... choice = schema.Choice(title=u'Choice', required=False, ... source=ChoiceSource()) >>> class WithChoice(object): ... implements(IWithChoice) ... def __init__(self, choice): ... self.choice = choice >>> with_choice = WithChoice('alpha') >>> xml = serialize('container', IWithChoice, with_choice) >>> print xml <container> <choice>alpha</choice> </container> >>> new_choice = WithChoice(None) >>> deserialize(xml, IWithChoice, new_choice) >>> new_choice.choice 'alpha' >>> with_choice = WithChoice(None) >>> xml = serialize('container', IWithChoice, with_choice) >>> print xml <container> <choice/> </container> >>> deserialize(xml, IWithChoice, new_choice) >>> new_choice.choice is None True
Set
Set fields are very similar to List fields:
>>> class IWithSet(interface.Interface): ... set = schema.Set(title=u'Set', required=False, ... value_type=schema.Choice(__name__='choice', ... source=ChoiceSource())) >>> class WithSet(object): ... implements(IWithSet) ... def __init__(self, set): ... self.set = set >>> with_set = WithSet(set(['alpha'])) >>> xml = serialize('container', IWithSet, with_set) >>> print xml <container> <set> <choice>alpha</choice> </set> </container> >>> with_set = WithSet(set(['alpha', 'beta'])) >>> xml = serialize('container', IWithSet, with_set) >>> print xml <container> <set> <choice>alpha</choice> <choice>beta</choice> </set> </container> >>> new_set = WithSet(None) >>> deserialize(xml, IWithSet, new_set) >>> new_set.set set(['alpha', 'beta'])
CHANGES
1.0 (2008-12-05)
Changed dependency on grokcore.component so that this becomes useful in straight Zope 3 applications as well.
Run tests against lxml 2.0.9.
0.10 (2008-03-10)
First checkin in svn.zope.org.
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