ContentProvider to send multipart/form-data messages
Use this provider to send a multipart form to the server. A multipart form is a message
containing a series of parts, where each part has a "control name" and its data. The data can
be any of the types allowed for
RequestMessage.Body.Data or another
Some servers require multiple parts under the same name to be in a nested multipart/mixed
part. To send nested parts, wrap the parts in a
MultipartProvider. For example,
to send a message as described at the very end of chapter 17 of the HTML 4.01 specification
for form data:
fps = FileProvider(["file1.txt","file2.gif"]); % get array of providers mp = MultipartProvider(fps); formProvider = MultipartFormProvider("submit-name","Larry","files",mp); req = RequestMessage('put',,formProvider); req.send(uri);
matlab.net.http.io.MultipartFormProvider class is a
provider = MultipartFormProvider(
"multipart/form-data" content specified by one or more
name-part pair arguments.
Part is form-data containing a
Name and its contents. The
Part arguments can be
any of the types supported by
MultipartProvider, including other
Part is an array, it is equivalent to repeating the
Name,Part for each element of the array. For example, the
is equivalent to:
Names — Part names
Part names, specified as a string.
Parts — Message body parts
Parts of the message body, specified as a cell array of one or more of these values:
This treats each element of the array as a part. Not a cell array.
This method must have the signature of
Any other type
If the type does not match any of these types and is not a function
handle, then it is treated as if it was present in the
Header — Header fields of message or part
matlab.net.http.HeaderField.empty (default) |
Header fields of the message or part, specified as a vector of one or more
This property is only used by subclass authors. MATLAB sets this property before calling the provider's
method. For non-multipart messages, MATLAB initializes this property to the contents of
Request.Header, minus any
empty-valued fields. The
ContentProvider uses this property to add header
fields that describe the data to be sent, or to add parameters to header fields already
in the message. In a delegate for a
MultipartProvider, MATLAB initializes this property to header fields that the delegating provider
intends to insert for the part. Delegates can modify or change these fields.
Upon return from the provider's
complete method, if this not a
multipart message, then MATLAB reads this property and merges its contents into the header of
Request. Fields in this
Names that do not already appear in
Request.Header are added to the end of
Request.Header. If a field in this
Name that is the same as one in
Request.Header, and both have nonempty
If the one in
GenericField, then ignore the one in
If the one in
Request.Headeris not a
GenericField, then replace it with the one in
If one or both of these has an empty
Value, then the field is
Request.Header and it is not added as part of normal
If this is a delegate of a
MultipartProvider, then the entire contents
Header is used as the header of the part. Multipart
delegates must not assume that
Request.Header contains any fields
pertaining to their own
Header. A provider can determine whether it
is a multipart delegate by checking whether
MyDelegator is a
MultipartProvider, though this test is unlikely to be needed.
MATLAB reads this property only on return from calling the provider's
complete method. Changes to this array are ignored once MATLAB calls
Class authors should be aware that their subclasses might have added fields to this
Header (in their
complete method) before
complete in their superclass. It is best to preserve such
fields and not to add fields with the same names. However, adding a parameter to a field
is permissible. For example, a superclass can add a charset parameter to an existing
Content-Type field that does not already have one.
ForceChunked — Indicate whether to force chunked transfer coding
false (default) |
Indicate whether to force chunked transfer coding, specified as boolean. This property is of interest only to subclass authors, and is applicable only to providers that are not multipart delegates. Subclasses set
ForceChunked to control whether contents should be sent using chunked transfer coding. If
false (default), MATLAB decides whether to send the contents chunked, based on whether it knows the content length at the time the message is ready to be sent:
If MATLAB knows the content length (which is the case if the message contains a Content-Length field, or if this provider's
expectedContentLengthmethod returned a number), then MATLAB decides whether to send it chunked or not.
If MATLAB does not know the content length (no Content-Length field in the header and
expectedContentLengthreturned empty), then MATLAB always sends the message chunked.
true, then MATLAB sends the message chunked regardless of whether it knows the content length, unless the known length is smaller than the chunk size. If this property is
true, then the message must not contain a Content-Length field, because HTTP does not allow a chunked message to have a Content-Length field. However, you can still return a nonzero value in the
expectedContentLength method if you want MATLAB to verify that you are returning the expected length of data.
When MATLAB chooses to send the message chunked, the size of each chunk is equal to the length of data returned by
MATLAB reads this value after calling the
complete method, before calling
start. It does not set this field.
Request — Request message to send
Request message to send, specified as a
This property is used only by subclass authors. The
methods set this property to the
RequestMessage in whose
Body this provider has been placed, before calling any other
methods in this provider, and before adding any additional header fields or validating
the message. The provider can examine this message to see what was contained in the
Delegates see the same value for this property as the delegator.
ContentProviders should be aware that, if they are delegates, they
are not necessarily providing the entire body of the request message, so they should not
assume that header fields in this Request are pertinent to the data they are providing.
Usually, delegates should ignore header fields in this request relevant to the data,
such as Content-Type.
If the provider wishes to add any header fields to this message, or to modify existing
ones, it should do so in its
method by adding those fields to the
Header property. The caller of
RequestMessage or a delegating provider)
determines what to do with those fields.
RequestMessage.complete always copy these fields to the
Header of the
RequestMessage. A delegating
provider can copy the fields to its own
Header property or insert
them into the message (as in the case of
MultipartProvider). For more
information, see the Header property.
This property is read-only.
Subtype — Provider subtype
"mixed" (default) | string
Provider subtype, specified as a string. The default value
"mixed" adds a Content-Type header set to
"multipart/mixed" to the message, plus appropriate parameters.
Subclasses can alter this value in the constructor or the
method. This value appears in the Content-Type after
ContentProvider to which this provider is delegating
matlab.net.http.io.ContentProvider | empty
ContentProvider to which this provider is delegating, specified as a
matlab.net.http.io.ContentProvider object. This property is set in the calling provider (the delegator) by the
delegateTo method to indicate the current delegated provider. If there is no current delegation, then the value is empty.
complete methods set this property to empty.
ContentProvider that delegated to this provider
matlab.net.http.io.ContentProvider.empty (default) |
ContentProvider that delegated to this provider, specified as a
ContentProvider delegates responsibility for sending all or a portion of the message data to another provider, then this property identifies the delegating provider to the delegate. For example, a
MultipartProvider delegates parts of the message to other providers, so it inserts a handle to itself in each delegate. Otherwise,
MyDelegator is empty. The
delegateTo method sets this property in the delegate.
|Next buffer of data to send in multipart HTTP request message|
Specialized Operators and Functions
These methods specialize standard MATLAB operators and functions and inherited methods for objects in this class.
Provider information as string
Display provider information
|Complete HTTP header for MultipartProvider|
|Preferred buffer size for ContentProvider|
|Content length of ContentProvider|
|Start data transfer from MultipartProvider|
|Indicate whether ImageProvider is restartable|
|Indicate whether ImageProvider is reusable|
|Delegate to another provider|
Introduced in R2018a