matlab.net.http.io.MultipartFormProvider - ContentProvider to send multipart/form-data messages - MATLAB (original) (raw)

Namespace: matlab.net.http.io
Superclasses: matlab.net.http.io.MultipartProvider

ContentProvider to send multipart/form-data messages

Description

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 anotherContentProvider.

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);

The matlab.net.http.io.MultipartFormProvider class is a handle class.

Creation

Description

provider = MultipartFormProvider(`Name,Part`) creates "multipart/form-data" content specified by one or more name-part pair arguments. Part is form-data containing aName and its contents. The Part arguments can be any of the types supported by MultipartProvider, including otherContentProvider objects.

If a Part is an array, it is equivalent to repeating theName,Part for each element of the array. For example, the statement:

MultipartFormProvider("name",FileProvider(["file1" "file2"]))

is equivalent to:

MultipartFormProvider("name",FileProvider("file1"),"name",FileProvider("file2"));

Properties

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Public Properties

Part names, specified as a string.

Attributes:

Parts of the message body, specified as a cell array of one or more of these values:

Attributes:

Header fields of the message or part, specified as a vector of one or morematlab.net.http.HeaderField objects.

This property is only used by subclass authors. MATLAB sets this property before calling the provider's complete method. For non-multipart messages, MATLAB initializes this property to the contents ofRequest.Header, minus any matlab.net.http.field.GenericFields or 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 ofRequest. Fields in this Header withNames that do not already appear inRequest.Header are added to the end ofRequest.Header. If a field in this Header has a Name that is the same as one inRequest.Header, and both have nonemptyValues, then:

• If the one in Request.Header is aGenericField, then ignore the one inHeader.
• If the one in Request.Header is not aGenericField, then replace it with the one inHeader.

If one or both of these has an empty Value, then the field is removed from Request.Header and it is not added as part of normal message completion.

If this is a delegate of a MultipartProvider, then the entire contents of this 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 aMultipartProvider, though this test is unlikely to be needed.

MATLAB reads this property only on return from calling the provider'scomplete method. Changes to this array are ignored once MATLAB calls start.

Class authors should be aware that their subclasses might have added fields to thisHeader (in their complete method) before calling 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.

Attributes:

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 expectedContentLength method 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 expectedContentLength returned empty), then MATLAB always sends the message chunked.

If ForceChunked is 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 getData.

MATLAB reads this value after calling the complete method, before calling start. It does not set this field.

Attributes:

Request message to send, specified as a matlab.net.http.RequestMessage object.

This property is used only by subclass authors. TheRequestMessage.send and RequestMessage.complete methods set this property to the RequestMessage in whoseBody 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 original request.

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 complete method by adding those fields to the Header property. The caller ofcomplete (RequestMessage or a delegating provider) determines what to do with those fields. RequestMessage.send andRequestMessage.complete always copy these fields to theHeader 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.

Attributes:

Protected Properties

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 complete method. This value appears in the Content-Type after"multipart/".

Attributes:

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.

The complete methods set this property to empty.

Attributes:

ContentProvider that delegated to this provider, specified as a matlab.net.http.io.ContentProvider object.

If 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.

Attributes:

Methods

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These methods specialize standard MATLAB operators and functions and inherited methods for objects in this class.

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Version History

Introduced in R2018a