Request Content Types

If your HTTP request has a payload and you do not specify the content type, HttpCommand will attempt to determine whether to use a content type of 'application/json' or 'application/x-www-form-urlencoded'.

This may be fine for interactively tinkering in the APL session. But when running HttpCommand under program control you should explicitly specify the content type for the payload by either setting ContentType or adding a content-type header.

The exception to this is when using GetJSON which is specifically intended to interact with JSON-based web services and will use a default content type of application/json.

Special Treatment of Content Type application/json

If you specify a content type of 'application/json', HttpCommand will automatically convert a non-JSON Params setting to JSON. In the rare case where Params is an APL character vector that happens to represent valid JSON, you should convert it yourself using 1 ⎕JSON.

Special Treatment of Content Type multipart/form-data

Content type multipart/form-data is commonly used to transfer files to a server or to send multiple types of content in the request payload. If you specify a content type of 'multipart/form-data':

• Params must be a namespace with named elements.
• Each element in Params consists of the data for the element optionally followed by a content type for the element.
• To send a file, prefix the file name with either:
  • @ to upload the file's content and its name
  • < to upload just the file's content
• If you do not specify a content type for the file, HttpCommand will use a content type of 'text/plain' if the extension of the file is .txt, otherwise it will use a content type of 'application/octet-stream'.

In the example below:

• Extra newlines have been removed for compactness.
• The file /tmp/foo.txt contains Hello World.
• We create 4 parts to be sent with the request:
  • a simple string
  • a named file - both the content and file name will be sent
  • an unnamed file - only the content will be sent
  • a JSON array (with content type 'application/json')

      h←HttpCommand.New 'post' 'someurl.com'
      p←⎕NS ''                     ⍝ create a namespace
      p.string←'/tmp/foo.txt'       ⍝ just a value
      p.namedfile←'@/tmp/foo.txt'   ⍝ @ = include the file name
      p.unnamedfile←'</tmp/foo.txt' ⍝ < = do not include the file name
      p.json←'[1,2,3]' 'application/json' ⍝ value and content type
      h.Params←p                    ⍝ assign the request Params
      h.ContentType←'multipart/form-data' ⍝ 
      h.Show
POST / HTTP/1.1
Host: someurl.com                                                                                              
User-Agent: Dyalog-HttpCommand/5.6.0
Accept: */*
Accept-Encoding: gzip, deflate
Content-Type: multipart/form-data; boundary=rgt7DIuxBqLFsveaLM0fBcR7gdvahhUfbtmuQ9UMEZvv9kDVrd
Content-Length: 631

--rgt7DIuxBqLFsveaLM0fBcR7gdvahhUfbtmuQ9UMEZvv9kDVrd
Content-Disposition: form-data; name="json"
Content-Type: application/json                                                                                              
[1,2,3]

--rgt7DIuxBqLFsveaLM0fBcR7gdvahhUfbtmuQ9UMEZvv9kDVrd
Content-Disposition: form-data; name="namedfile"; filename="foo.txt"
Content-Type: text/plain
Hello World

--rgt7DIuxBqLFsveaLM0fBcR7gdvahhUfbtmuQ9UMEZvv9kDVrd
Content-Disposition: form-data; name="string"                                                 
/tmp/foo.txt

--rgt7DIuxBqLFsveaLM0fBcR7gdvahhUfbtmuQ9UMEZvv9kDVrd
Content-Disposition: form-data; name="unnamedfile"
Content-Type: text/plain
Hello World

--rgt7DIuxBqLFsveaLM0fBcR7gdvahhUfbtmuQ9UMEZvv9kDVrd--