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239 lines
8.6 KiB
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239 lines
8.6 KiB
Text
==================================
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Uploaded Files and Upload Handlers
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==================================
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.. module:: django.core.files.uploadedfile
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:synopsis: Classes representing uploaded files.
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Uploaded files
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==============
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.. class:: UploadedFile
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During file uploads, the actual file data is stored in :attr:`request.FILES
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<django.http.HttpRequest.FILES>`. Each entry in this dictionary is an
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``UploadedFile`` object (or a subclass) -- a simple wrapper around an uploaded
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file. You'll usually use one of these methods to access the uploaded content:
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.. method:: UploadedFile.read()
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Read the entire uploaded data from the file. Be careful with this method:
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if the uploaded file is huge it can overwhelm your system if you try to
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read it into memory. You'll probably want to use ``chunks()`` instead; see
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below.
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.. method:: UploadedFile.multiple_chunks(chunk_size=None)
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Returns ``True`` if the uploaded file is big enough to require reading in
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multiple chunks. By default this will be any file larger than 2.5 megabytes,
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but that's configurable; see below.
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.. method:: UploadedFile.chunks(chunk_size=None)
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A generator returning chunks of the file. If ``multiple_chunks()`` is
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``True``, you should use this method in a loop instead of ``read()``.
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In practice, it's often easiest simply to use ``chunks()`` all the time.
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Looping over ``chunks()`` instead of using ``read()`` ensures that large
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files don't overwhelm your system's memory.
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Here are some useful attributes of ``UploadedFile``:
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.. attribute:: UploadedFile.name
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The name of the uploaded file (e.g. ``my_file.txt``).
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.. attribute:: UploadedFile.size
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The size, in bytes, of the uploaded file.
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.. attribute:: UploadedFile.content_type
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The content-type header uploaded with the file (e.g. :mimetype:`text/plain`
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or :mimetype:`application/pdf`). Like any data supplied by the user, you
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shouldn't trust that the uploaded file is actually this type. You'll still
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need to validate that the file contains the content that the content-type
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header claims -- "trust but verify."
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.. attribute:: UploadedFile.content_type_extra
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A dictionary containing extra parameters passed to the ``content-type``
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header. This is typically provided by services, such as Google App Engine,
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that intercept and handle file uploads on your behalf. As a result your
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handler may not receive the uploaded file content, but instead a URL or
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other pointer to the file. (see `RFC 2388`_ section 5.3).
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.. _RFC 2388: https://www.ietf.org/rfc/rfc2388.txt
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.. attribute:: UploadedFile.charset
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For :mimetype:`text/*` content-types, the character set (i.e. ``utf8``)
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supplied by the browser. Again, "trust but verify" is the best policy here.
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.. note::
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Like regular Python files, you can read the file line-by-line simply by
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iterating over the uploaded file:
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.. code-block:: python
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for line in uploadedfile:
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do_something_with(line)
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Lines are split using `universal newlines`_. The following are recognized
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as ending a line: the Unix end-of-line convention ``'\n'``, the Windows
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convention ``'\r\n'``, and the old Macintosh convention ``'\r'``.
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.. _universal newlines: https://www.python.org/dev/peps/pep-0278
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Subclasses of ``UploadedFile`` include:
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.. class:: TemporaryUploadedFile
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A file uploaded to a temporary location (i.e. stream-to-disk). This class
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is used by the
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:class:`~django.core.files.uploadhandler.TemporaryFileUploadHandler`. In
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addition to the methods from :class:`UploadedFile`, it has one additional
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method:
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.. method:: TemporaryUploadedFile.temporary_file_path()
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Returns the full path to the temporary uploaded file.
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.. class:: InMemoryUploadedFile
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A file uploaded into memory (i.e. stream-to-memory). This class is used
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by the :class:`~django.core.files.uploadhandler.MemoryFileUploadHandler`.
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Built-in upload handlers
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========================
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.. module:: django.core.files.uploadhandler
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:synopsis: Django's handlers for file uploads.
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Together the :class:`MemoryFileUploadHandler` and
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:class:`TemporaryFileUploadHandler` provide Django's default file upload
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behavior of reading small files into memory and large ones onto disk. They
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are located in ``django.core.files.uploadhandler``.
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.. class:: MemoryFileUploadHandler
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File upload handler to stream uploads into memory (used for small files).
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.. class:: TemporaryFileUploadHandler
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Upload handler that streams data into a temporary file using
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:class:`~django.core.files.uploadedfile.TemporaryUploadedFile`.
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.. _custom_upload_handlers:
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Writing custom upload handlers
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==============================
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.. class:: FileUploadHandler
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All file upload handlers should be subclasses of
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``django.core.files.uploadhandler.FileUploadHandler``. You can define upload
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handlers wherever you wish.
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Required methods
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----------------
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Custom file upload handlers **must** define the following methods:
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.. method:: FileUploadHandler.receive_data_chunk(raw_data, start)
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Receives a "chunk" of data from the file upload.
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``raw_data`` is a byte string containing the uploaded data.
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``start`` is the position in the file where this ``raw_data`` chunk
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begins.
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The data you return will get fed into the subsequent upload handlers'
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``receive_data_chunk`` methods. In this way, one handler can be a
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"filter" for other handlers.
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Return ``None`` from ``receive_data_chunk`` to short-circuit remaining
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upload handlers from getting this chunk. This is useful if you're
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storing the uploaded data yourself and don't want future handlers to
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store a copy of the data.
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If you raise a ``StopUpload`` or a ``SkipFile`` exception, the upload
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will abort or the file will be completely skipped.
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.. method:: FileUploadHandler.file_complete(file_size)
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Called when a file has finished uploading.
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The handler should return an ``UploadedFile`` object that will be stored
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in ``request.FILES``. Handlers may also return ``None`` to indicate that
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the ``UploadedFile`` object should come from subsequent upload handlers.
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Optional methods
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----------------
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Custom upload handlers may also define any of the following optional methods or
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attributes:
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.. attribute:: FileUploadHandler.chunk_size
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Size, in bytes, of the "chunks" Django should store into memory and feed
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into the handler. That is, this attribute controls the size of chunks
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fed into ``FileUploadHandler.receive_data_chunk``.
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For maximum performance the chunk sizes should be divisible by ``4`` and
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should not exceed 2 GB (2\ :sup:`31` bytes) in size. When there are
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multiple chunk sizes provided by multiple handlers, Django will use the
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smallest chunk size defined by any handler.
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The default is 64*2\ :sup:`10` bytes, or 64 KB.
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.. method:: FileUploadHandler.new_file(field_name, file_name, content_type, content_length, charset, content_type_extra)
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Callback signaling that a new file upload is starting. This is called
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before any data has been fed to any upload handlers.
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``field_name`` is a string name of the file ``<input>`` field.
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``file_name`` is the filename provided by the browser.
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``content_type`` is the MIME type provided by the browser -- E.g.
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``'image/jpeg'``.
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``content_length`` is the length of the image given by the browser.
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Sometimes this won't be provided and will be ``None``.
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``charset`` is the character set (i.e. ``utf8``) given by the browser.
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Like ``content_length``, this sometimes won't be provided.
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``content_type_extra`` is extra information about the file from the
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``content-type`` header. See :attr:`UploadedFile.content_type_extra
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<django.core.files.uploadedfile.UploadedFile.content_type_extra>`.
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This method may raise a ``StopFutureHandlers`` exception to prevent
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future handlers from handling this file.
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.. method:: FileUploadHandler.upload_complete()
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Callback signaling that the entire upload (all files) has completed.
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.. method:: FileUploadHandler.handle_raw_input(input_data, META, content_length, boundary, encoding)
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Allows the handler to completely override the parsing of the raw
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HTTP input.
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``input_data`` is a file-like object that supports ``read()``-ing.
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``META`` is the same object as ``request.META``.
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``content_length`` is the length of the data in ``input_data``. Don't
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read more than ``content_length`` bytes from ``input_data``.
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``boundary`` is the MIME boundary for this request.
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``encoding`` is the encoding of the request.
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Return ``None`` if you want upload handling to continue, or a tuple of
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``(POST, FILES)`` if you want to return the new data structures suitable
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for the request directly.
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