matlab.net.http.HeaderField Class

Namespace: matlab.net.http

Header field of HTTP message

Description

Use the HeaderField class to implement a header field for an HTTP message. The class provides conversions between strings in the header and MATLAB^® objects, arrays, and structures. Although you can set the HeaderField properties to arbitrary values, HTTP header fields have constraints on the allowed characters.

The Name property defines the header field type. MATLAB provides subclasses for commonly used fields in the matlab.net.http.field namespace. To see a list of supported subclasses, call the HeaderField.displaySubclasses method.

Creation

Description

obj = matlab.net.http.HeaderField(name,value) creates a header field with the Name property set to name and the Value property set to value. Either argument can be an empty double, []. You can specify several argument pairs in any order as name1,value1,...,nameN,valueN. If the last value argument is missing, then HeaderField treats it as empty.

Properties

Name — Header field name

string | character vector

Header field name, specified as a string or character vector. Name determines the type of the field, which determines valid values for the Value property. If you set Name to [] or an empty string, then Value is [].

If this object is an instance of a subclass implementing a specific header field type, then that class enforces constraints on the Name property.

Example: 'Content-Type'

Attributes:

GetAccess	public
SetAccess	public

Value — Header field value

string | any type valid for Name

Header field value, specified as a string or any type valid for the Name property.

When you read this property, Value is a string representing the value in the field.

When you set this property, Value is any type acceptable to the field based on the Name property and/or the class of this object. The result is converted to a string. If a field type has a default value, set Value to an empty string ('' or string('')). If you specify an empty double, [], then the request message send and complete methods do not add this field to the message.

Example: 'text/html'

Attributes:

GetAccess	public
SetAccess	public
Dependent	true

Methods

Public Methods

convert	Convert header field value to MATLAB type
convertLike	Convert header field value like another header field
parse	Parse header field value and return as strings
addFields	Add fields to HeaderField array
removeFields	Remove fields from header field array
changeFields	Change existing values in HeaderField array
replaceFields	Change values in or add fields to array of HeaderFields
getFields	Return header fields matching name or class
eq	Compare two HeaderField arrays
displaySubclasses	Display supported HeaderField subclasses

Specialized Operators and Functions

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

isequal	Return true if two header field arrays are the same size and the corresponding elements are equal as described by the eq method.
string	Array of header fields as a string, as it appears in a message. Newline characters are inserted between the fields but not at the end of all the fields.
char	Array of header fields as a character vector, as described by the string method

Examples

Choose Header Field Constructor

To create a Content-Type header field, use either the HeaderField class or the ContentTypeField class constructor.

When you use the HeaderField class constructor, you specify the Name property as 'Content-Type'. However, if you misspell the field name, you might not find out about the error until the server rejects the message. Some servers silently ignore unknown field names.

f1 = matlab.net.http.HeaderField('Content-Type','text/plain');

Using the ContentTypeField class constructor is preferred because you cannot misspell the field name.

f2 = matlab.net.http.field.ContentTypeField('text/plain');

If the Value properties are the same, then the fields are equal, regardless of which constructor you use.

f1 == f2

ans =    1

Find Value in HTTP HeaderField Array

This example shows how to locate a specific header field Cache-Control in a response from mathworks.com.

Send a message to mathworks.com.

request = matlab.net.http.RequestMessage;
uri = matlab.net.URI('https://www.mathworks.com');
response = send(request,uri);

Search for Cache-Control and display the value.

field = response.getFields('Cache-Control');
value = field.Value

value = 
"max-age=14400"

Tips

• The HeaderField constructor creates fields of class HeaderField. To create a field of a class defined in the matlab.net.http.field namespace, use the subclass constructor instead. For a list of subclasses, call the HeaderField.displaySubclasses method.

  For example, the matlab.net.http.field.DateField subclass creates a Date header field. If you use the HeaderField class to create a Date field, the DateField class interprets and enforces the value, even though HeaderField is not an instance of DateField. Likewise, if you convert the field value to a MATLAB datetime value, the DateField.convert method is used.

• If the HeaderField constructor rejects the Name and Value arguments, use the GenericField class constructor instead.

Version History

Introduced in R2016b