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# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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"""Provides a factory class for generating dynamic messages."""
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#PY25 compatible for GAE.
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# Copyright 2012 Google Inc. All Rights Reserved.
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"""Provides a factory class for generating dynamic messages.
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The easiest way to use this class is if you have access to the FileDescriptor
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protos containing the messages you want to create you can just do the following:
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message_classes = message_factory.GetMessages(iterable_of_file_descriptors)
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my_proto_instance = message_classes['some.proto.package.MessageName']()
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__author__ = 'matthewtoia@google.com (Matt Toia)'
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from google.protobuf import descriptor_database
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from google.protobuf import descriptor_pool
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from google.protobuf import message
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class MessageFactory(object):
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"""Factory for creating Proto2 messages from descriptors in a pool."""
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def __init__(self, pool=None):
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"""Initializes a new factory."""
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self.pool = (pool or descriptor_pool.DescriptorPool(
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descriptor_database.DescriptorDatabase()))
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# local cache of all classes built from protobuf descriptors
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def GetPrototype(self, descriptor):
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A class describing the passed in descriptor.
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if descriptor.full_name not in self._classes:
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descriptor_name = descriptor.name
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if sys.version_info[0] < 3: ##PY25
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##!PY25 if str is bytes: # PY2
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descriptor_name = descriptor.name.encode('ascii', 'ignore')
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result_class = reflection.GeneratedProtocolMessageType(
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descriptor.name.encode('ascii', 'ignore'),
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(message.Message,),
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{'DESCRIPTOR': descriptor})
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{'DESCRIPTOR': descriptor, '__module__': None})
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# If module not set, it wrongly points to the reflection.py module.
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self._classes[descriptor.full_name] = result_class
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for field in descriptor.fields:
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if field.message_type:
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self.GetPrototype(field.message_type)
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for extension in result_class.DESCRIPTOR.extensions:
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if extension.containing_type.full_name not in self._classes:
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self.GetPrototype(extension.containing_type)
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extended_class = self._classes[extension.containing_type.full_name]
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extended_class.RegisterExtension(extension)
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return self._classes[descriptor.full_name]
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_DB = descriptor_database.DescriptorDatabase()
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_POOL = descriptor_pool.DescriptorPool(_DB)
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def GetMessages(self, files):
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"""Gets all the messages from a specified file.
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This will find and resolve dependencies, failing if the descriptor
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pool cannot satisfy them.
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files: The file names to extract messages from.
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A dictionary mapping proto names to the message classes. This will include
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any dependent messages as well as any messages defined in the same file as
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for file_name in files:
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file_desc = self.pool.FindFileByName(file_name)
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for name, msg in file_desc.message_types_by_name.iteritems():
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if file_desc.package:
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full_name = '.'.join([file_desc.package, name])
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result[full_name] = self.GetPrototype(
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self.pool.FindMessageTypeByName(full_name))
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# While the extension FieldDescriptors are created by the descriptor pool,
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# the python classes created in the factory need them to be registered
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# explicitly, which is done below.
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# The call to RegisterExtension will specifically check if the
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# extension was already registered on the object and either
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# ignore the registration if the original was the same, or raise
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# an error if they were different.
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for name, extension in file_desc.extensions_by_name.iteritems():
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if extension.containing_type.full_name not in self._classes:
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self.GetPrototype(extension.containing_type)
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extended_class = self._classes[extension.containing_type.full_name]
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extended_class.RegisterExtension(extension)
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_FACTORY = MessageFactory()
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file_protos: A sequence of file protos to build messages out of.
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A dictionary containing all the message types in the files mapping the
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fully qualified name to a Message subclass for the descriptor.
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for file_proto in file_protos:
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for file_proto in file_protos:
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for desc in _GetAllDescriptors(file_proto.message_type, file_proto.package):
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result[desc.full_name] = _FACTORY.GetPrototype(desc)
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def _GetAllDescriptors(desc_protos, package):
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"""Gets all levels of nested message types as a flattened list of descriptors.
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desc_protos: The descriptor protos to process.
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package: The package where the protos are defined.
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Each message descriptor for each nested type.
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for desc_proto in desc_protos:
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name = '.'.join((package, desc_proto.name))
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yield _POOL.FindMessageTypeByName(name)
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for nested_desc in _GetAllDescriptors(desc_proto.nested_type, name):
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A dictionary mapping proto names to the message classes. This will include
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any dependent messages as well as any messages defined in the same file as
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for file_proto in file_protos:
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_FACTORY.pool.Add(file_proto)
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return _FACTORY.GetMessages([file_proto.name for file_proto in file_protos])
added
removed
python/google/protobuf/message_factory.py
