Django2.0手册:Uploaded Files and Upload Handlers



Uploaded files¶

class UploadedFile[source]

During file uploads, the actual file data is stored in request.FILES. Each entry in this dictionary is an
UploadedFile object (or a subclass) — a simple wrapper around an uploaded
file. You’ll usually use one of these methods to access the uploaded content:

UploadedFile.read()

Read the entire uploaded data from the file. Be careful with this method:
if the uploaded file is huge it can overwhelm your system if you try to
read it into memory. You’ll probably want to use chunks() instead; see
below.

UploadedFile.multiple_chunks(chunk_size=None)

Returns True if the uploaded file is big enough to require reading in
multiple chunks. By default this will be any file larger than 2.5 megabytes,
but that’s configurable; see below.

UploadedFile.chunks(chunk_size=None)

A generator returning chunks of the file. If multiple_chunks() is
True, you should use this method in a loop instead of read().

In practice, it’s often easiest simply to use chunks() all the time.
Looping over chunks() instead of using read() ensures that large
files don’t overwhelm your system’s memory.

Here are some useful attributes of UploadedFile:

UploadedFile.name

The name of the uploaded file (e.g. my_file.txt).

UploadedFile.size

The size, in bytes, of the uploaded file.

UploadedFile.content_type

The content-type header uploaded with the file (e.g. text/plain
or application/pdf). Like any data supplied by the user, you
shouldn’t trust that the uploaded file is actually this type. You’ll still
need to validate that the file contains the content that the content-type
header claims — “trust but verify.”

UploadedFile.content_type_extra

A dictionary containing extra parameters passed to the content-type
header. This is typically provided by services, such as Google App Engine,
that intercept and handle file uploads on your behalf. As a result your
handler may not receive the uploaded file content, but instead a URL or
other pointer to the file. (see RFC 2388 section 5.3).

UploadedFile.charset

For text/* content-types, the character set (i.e. utf8)
supplied by the browser. Again, “trust but verify” is the best policy here.

Note

Like regular Python files, you can read the file line-by-line simply by
iterating over the uploaded file:

for line in uploadedfile:
    do_something_with(line)

Lines are split using universal newlines. The following are recognized
as ending a line: the Unix end-of-line convention '\n', the Windows
convention '\r\n', and the old Macintosh convention '\r'.

Subclasses of UploadedFile include:

class TemporaryUploadedFile[source]

A file uploaded to a temporary location (i.e. stream-to-disk). This class
is used by the
TemporaryFileUploadHandler. In
addition to the methods from UploadedFile, it has one additional
method:

TemporaryUploadedFile.temporary_file_path()[source]

Returns the full path to the temporary uploaded file.

class InMemoryUploadedFile[source]

A file uploaded into memory (i.e. stream-to-memory). This class is used
by the MemoryFileUploadHandler.

Built-in upload handlers¶

Together the MemoryFileUploadHandler and
TemporaryFileUploadHandler provide Django’s default file upload
behavior of reading small files into memory and large ones onto disk. They
are located in django.core.files.uploadhandler.

class MemoryFileUploadHandler[source]

File upload handler to stream uploads into memory (used for small files).

class TemporaryFileUploadHandler[source]

Upload handler that streams data into a temporary file using
TemporaryUploadedFile.

Writing custom upload handlers¶

class FileUploadHandler[source]

All file upload handlers should be subclasses of
django.core.files.uploadhandler.FileUploadHandler. You can define upload
handlers wherever you wish.

Required methods¶

Custom file upload handlers must define the following methods:

FileUploadHandler.receive_data_chunk(raw_data, start)[source]

Receives a “chunk” of data from the file upload.

raw_data is a byte string containing the uploaded data.

start is the position in the file where this raw_data chunk
begins.

The data you return will get fed into the subsequent upload handlers’
receive_data_chunk methods. In this way, one handler can be a
“filter” for other handlers.

Return None from receive_data_chunk to short-circuit remaining
upload handlers from getting this chunk. This is useful if you’re
storing the uploaded data yourself and don’t want future handlers to
store a copy of the data.

If you raise a StopUpload or a SkipFile exception, the upload
will abort or the file will be completely skipped.

FileUploadHandler.file_complete(file_size)[source]

Called when a file has finished uploading.

The handler should return an UploadedFile object that will be stored
in request.FILES. Handlers may also return None to indicate that
the UploadedFile object should come from subsequent upload handlers.

Optional methods¶

Custom upload handlers may also define any of the following optional methods or
attributes:

FileUploadHandler.chunk_size

Size, in bytes, of the “chunks” Django should store into memory and feed
into the handler. That is, this attribute controls the size of chunks
fed into FileUploadHandler.receive_data_chunk.

For maximum performance the chunk sizes should be divisible by 4 and
should not exceed 2 GB (231 bytes) in size. When there are
multiple chunk sizes provided by multiple handlers, Django will use the
smallest chunk size defined by any handler.

The default is 64*210 bytes, or 64 KB.

FileUploadHandler.new_file(field_name, file_name, content_type, content_length, charset, content_type_extra)[source]

Callback signaling that a new file upload is starting. This is called
before any data has been fed to any upload handlers.

field_name is a string name of the file <input> field.

file_name is the filename provided by the browser.

content_type is the MIME type provided by the browser — E.g.
'image/jpeg'.

content_length is the length of the image given by the browser.
Sometimes this won’t be provided and will be None.

charset is the character set (i.e. utf8) given by the browser.
Like content_length, this sometimes won’t be provided.

content_type_extra is extra information about the file from the
content-type header. See UploadedFile.content_type_extra.

This method may raise a StopFutureHandlers exception to prevent
future handlers from handling this file.

FileUploadHandler.upload_complete()[source]

Callback signaling that the entire upload (all files) has completed.

FileUploadHandler.handle_raw_input(input_data, META, content_length, boundary, encoding)[source]

Allows the handler to completely override the parsing of the raw
HTTP input.

input_data is a file-like object that supports read()-ing.

META is the same object as request.META.

content_length is the length of the data in input_data. Don’t
read more than content_length bytes from input_data.

boundary is the MIME boundary for this request.

encoding is the encoding of the request.

Return None if you want upload handling to continue, or a tuple of
(POST, FILES) if you want to return the new data structures suitable
for the request directly.