Package: z3c.blobfile
Blob FileThis package provides an implementation of zope.app.file.interfaces.IFile
which uses the Blob support introduced in ZODB 3.8. It’s main purpose
is to provide an easy migration path for existing instances. For more
advanced file implementations see zope.file and z3c.extfile.The standard implementation in zope.app.file uses chunk objects to
break big files into manageable parts. These chunks flow the server caches
whereas blobs are directly consumed by the publisher. The main difference
between this blob implementation and the old zope.app.file implementation
can be seen in a replacement of the chunk objects by Blobs.Detailed DocumentationBlob File ImplementationThis implementation of zope.app.file.interfaces.IFile takes advantage
of the new ZODB blob support and tries to be completely backward compatible to
the existing file implementation in zope.app.file.Compatibility with zope.app.file.FileThe following tests mimic exactly the tests of the zope.app.file package.Let’s test the constructor:>>> from zope.app.file import File, Image>>> file = File()
>>> file.contentType
''
>>> file.data
''>>> file = File('Foobar')
>>> file.contentType
''
>>> file.data
'Foobar'>>> file = File('Foobar', 'text/plain')
>>> file.contentType
'text/plain'
>>> file.data
'Foobar'>>> file = File(data='Foobar', contentType='text/plain')
>>> file.contentType
'text/plain'
>>> file.data
'Foobar'Let’s test the mutators:>>> file = File()
>>> file.contentType = 'text/plain'
>>> file.contentType
'text/plain'>>> file.data = 'Foobar'
>>> file.data
'Foobar'>>> file.data = None
Traceback (most recent call last):
...
TypeError: Cannot set None data on a file.Let’s test large data input:>>> file = File()Insert as string:>>> file.data = 'Foobar'*60000
>>> file.getSize()
360000
>>> file.data == 'Foobar'*60000
TrueInsert data as FileChunk:>>> from zope.app.file.file import FileChunk
>>> fc = FileChunk('Foobar'*4000)
>>> file.data = fc
>>> file.getSize()
24000
>>> file.data == 'Foobar'*4000
TrueInsert data from file object:>>> import cStringIO
>>> sio = cStringIO.StringIO()
>>> sio.write('Foobar'*100000)
>>> sio.seek(0)
>>> file.data = sio
>>> file.getSize()
600000
>>> file.data == 'Foobar'*100000
TrueLast, but not least, verify the interface:>>> from zope.interface.verify import verifyClass
>>> zope.app.file.interfaces.IFile.implementedBy(File)
True
>>> verifyClass(zope.app.file.interfaces.IFile, File)
TrueTest of Filerepresentation Adapters>>> from zope.app.file.file import FileReadFile
>>> file = File()
>>> content = "This is some file\\ncontent."
>>> file.data = content
>>> file.contentType = "text/plain"
>>> FileReadFile(file).read() == content
True
>>> FileReadFile(file).size() == len(content)
True>>> from zope.app.file.file import FileWriteFile
>>> file = File()
>>> content = "This is some file\\ncontent."
>>> FileWriteFile(file).write(content)
>>> file.data == content
TrueEvolution of Existing FilesPlease note that the following code is experimental. The code should not be
used in production without careful testing. Backup your Data.fs and uncomment
the following lines in the configure.zcml if you want to replace exiting
zope.app.file.File instances.<utilitycomponent=”.generations.BlobFileSchemaManager”
name=”z3c.blobfile”
/>Let’s assume that you have already an existing database with zope.app.file
content types:>>> from z3c.blobfile import testing
>>> root = getRootFolder()>>> root[u'file'] = File('A text file', contentType='text/plain')
>>> root[u'image'] = Image(testing.zptlogo)Since the evolve step looks for implementations of IFile we also must
provide a way to recognize other implementations than zope.app.file.File and
Image. Let’s add a nonsense implementation as an example:>>> root[u'custom'] = testing.MyFile()Note that we cannot assume that these objects exist in isolation. Many of
them probably are annotated, indexed, some even may be registered as utility
etc. The evolution step throws the standard events when the objects
are replaced and it’s up the application that this replacement is recognized
accordingly. If your application has special needs you may subscribe to the
FileReplacedEvent.We will not test all relations to all other objects, since this is largely
application dependent. Here we only take the ZopeDublinCore timestamps as
an example that our evolution step leaves as many things untouched as possible.>>> from zope.dublincore.interfaces import IZopeDublinCore
>>> import datetime>>> IZopeDublinCore(root[u'file']).created = datetime.datetime.utcnow()
>>> t1 = IZopeDublinCore(root[u'file']).created
>>> IZopeDublinCore(root[u'file']).title = u'No evolution'Now we perform the basic evolution steps. Since we expect some warning logs
we need>>> from zope.testing.loggingsupport import InstalledHandler
>>> import logging
>>> log_handler = InstalledHandler('z3c.blobfile.generations')>>> from z3c.blobfile.generations.evolve1 import evolveZopeAppFile
>>> evolveZopeAppFile(root)
>>> transaction.commit()>>> for record in log_handler.records:
...     print record.getMessage()
Unknown ...interfaces.IFile implementation z3c.blobfile.testing.MyFileAfter the evolution step the class types have changed to the z3c.blobfile
implementations:>>> import z3c.blobfile
>>> isinstance(root[u'file'], z3c.blobfile.file.File)
True
>>> isinstance(root[u'image'], z3c.blobfile.image.Image)
TrueOnly the custom implementations remain untouched:>>> isinstance(root[u'custom'], testing.MyFile)
TrueThe file data remain the same …>>> root[u'file'].data
'A text file'
>>> root[u'file'].contentType
'text/plain'>>> root[u'image'].data == testing.zptlogo
Trueand so do the annotations:>>> IZopeDublinCore(root[u'file']).created == t1
True
>>> IZopeDublinCore(root[u'file']).title
u'No evolution'Even implementation details like the _data attribute still work:>>> root[u'file']._data
'A text file'CopyingLet’s check that blob files can be copied successfully. This
functionality requires the new “zope.copy” package and the
version of zope.copypastemove that uses zope.copy (>=3.5.1).>>> from zope.copy import copy
>>> file = z3c.blobfile.file.File()
>>> file.data = u'hello, world'
>>> image = z3c.blobfile.file.File()
>>> image.data = 'some image bytes'
>>> transaction.commit()>>> file_copy = copy(file)
>>> file_copy.data == file.data
True>>> image_copy = copy(image)
>>> image_copy.data == image.data
TrueCHANGES0.1.5 (2011-02-11)Put a ceiling (64k) on the number of info bytes read and read those bytes in
one shot.Bug: Correctly detect the dimensions of JPEG images with the dimensions
in a position greater than IMAGE_INFO_BYTES.Made tests compatible with ZODB 3.9.0.1.4 (2009-03-03)Add copy hook for zope.copy to fix blob file/image copying.Change package’s mailing list address to zope-dev at zope.org
instead of retired zope3-dev.0.1.3 (2008-10-20)Bug: Don’t get/set image data twice on Image initialization.Cache file size and invalidate it on write access.Download file/image using new openDetached method that provides
read-only file-like access to the blob, detached from the database
connection.0.1.2 (2008-09-11)Bug: Set i18n domain in “overrides.zcml” to avoid warnings.Don’t expose Blob implementation details in add/upload forms. Also, “zope”
translation domain has no translations for “Upload a File (Blob)”, it just
has “Upload a File” translations, so use it.0.1.1 (2008-09-08)Bug: Register zope.app.wsgi.fileresult.FileResult as an adapter for BlobFile,
making optimized file views really work.Bug: Also use optimized file view for z3c.blobfile.image.Image.Bug: Make blob versions of File and Image implement IBlobFile and
IBlobImage interfaces respectively. This enables z3c.blobfile’s views.Bug: Use local ZopeMessageFactory. This fixes import error on Zope 2.100.1.0 (2008-02-27)Initial Release