HTTP Request

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4D v16.3

HTTP Request


HTTP Request ( httpMethod ; url ; contents ; response {; headerNames ; headerValues}{; *} ) -> Function result

Parameter	Type	Description
httpMethod	Text	HTTP method for request
url	Text	URL to which to send the request
contents	Text, BLOB, Picture, Object	Contents of request body
response	Text, BLOB, Picture, Object	Result of request
headerNames	Text array	Header names of the request
		Returned header names
headerValues	Text array	Header values of the request
		Returned header values
*	Operator	If passed, connection is maintained (keep-alive) If omitted, connection is closed automatically
Function result	Longint	HTTP status code

Description

The HTTP Request command enables all types of HTTP requests to be sent to a specific URL and processes the HTTP server response.

Pass the HTTP method of the request in the httpMethod parameter. You can use one of the following constants, found in the HTTP Client theme:

Constant	Type	Value	Comment
HTTP DELETE method	String	DELETE	See RFC 2616
HTTP GET method	String	GET	See RFC 2616. Same as using HTTP Get command.
HTTP HEAD method	String	HEAD	See RFC 2616
HTTP OPTIONS method	String	OPTIONS	See RFC 2616
HTTP POST method	String	POST	See RFC 2616
HTTP PUT method	String	PUT	See RFC 2616
HTTP TRACE method	String	TRACE	See RFC 2616

Pass the URL where you want the request sent in the url parameter. The syntax to use is:

http://[{user}:[{password}]@]host[:{port}][/{path}][?{queryString}]

For example, you can pass the following strings:

    http://www.myserver.com
    http://www.myserver.com/path
    http://www.myserver.com/path?name="jones"
    https://www.myserver.com/login (*)
    http://123.45.67.89:8083
    http://john:smith@123.45.67.89:8083

(*) During HTTPS requests, authority of the certificate is not checked.

Pass the body of the request in the contents parameter. Data passed in this parameter depends on the HTTP method of the request.
You can send data of the Text, BLOB, Picture or Object type. When the content-type is not specified, the following types are used:

for text: text/plain - UTF8
for BLOBs: application/byte-stream
for pictures: known MIME type (best for Web).
for C_OBJECT objects: application/json

After command execution, the response parameter receives the result of the request returned by the server. This result corresponds to the body of the response, with no headers.
You can pass different types of variables in response:

Text: When the result is expected to be text (see note below).
BLOB: When the result is expected to be in binary
Picture: When the result is expected to be a picture.
C_OBJECT Object: When the result is expected to be an object.

Note: When a text variable is passed in response, 4D will try to decode the data returned from the server. 4D first tries to retrieve the charset from the content-type header, then from the content using a BOM, and finally looks for any http-equiv charset (in html content) or encoding (for xml) attribute. If no charset can be detected, 4D will attempt to decode the response in ANSI. If the conversion fails, the resulting text will be empty. If you are unsure whether the server returns a charset information or a BOM, but you know the encoding, it is more accurate to pass response in BLOB and call Convert to text.

When you pass a C_OBJECT type variable in the response parameter, if the request returns a result with an "application/json" (or "something/json") content-type, 4D attempts to parse the JSON content in order to generate the object.

If the result returned by the server does not correspond to the response variable type, it is left blank and the OK system variable is set to 0.

In headerNames and headerValues, you pass arrays containing the names and values of the request headers.
After this method is executed, these arrays contain the names and values of headers returned by the HTTP server. More specifically, this lets you manage cookies.

The * parameter enables the keep-alive mechanism for the server connection. By default, if this parameter is omitted, keep-alive is not enabled.

The command returns a standard HTTP status code (200=OK and so on) as returned by the server. The list of HTTP status codes is provided in RFC 2616.
If you are unable to connect to the server for a reason related to the network (DNS Failed, Server not reachable...), the command returns 0 and an error is generated. You can intercept errors using an error-handling method installed by the ON ERR CALL command.

Example 1

Requesting for a record deletion from a remote database:

 C_TEXT($response)

 $body_t:="{record_id:25}"

 $httpStatus_l:=HTTP Request(HTTP DELETE method;"database.example.com";$body_t;$response)

Note: You have to process the request appropriately on the remote server, HTTP Request only handles the request and the returned result.

Example 2

Requesting to add a record to a remote database:

 C_TEXT($response)

 $body_t:="{fName:'john',fName:'Doe'}"

 $httpStatus_l:=HTTP Request(HTTP PUT method;"database.example.com";$body_t;$response)

Note: You have to process the request appropriately on the remote server, HTTP Request only handles the request and the returned result.

Example 3

Request to add a record in JSON to a remote database::

 C_OBJECT($content)

 OB SET($content;"lastname";"Doe";"firstname";"John")

 $result:=HTTP Request(HTTP PUT method;"database.example.com";$content;$response)