HTTP Request Structure

HTTP requests are made up of four parts. Take this example client request to a FHIR API:

1) Method - the action to be performed on a resource

The method indicates the action to be performed on a resource within the API.

With Iguana’s net.http.* library, you can invoke different HTTP methods:

net.http.get{} - query or retrieve resources.
net.http.post{} - to add or create a resource.
net.http.put{} - update an existing resource.
net.http.delete{} - remove a resource.

2) Endpoint - the URL where the resource is found

The URL defines where the client can access the desired resources - for example the Patient resource.

url='http://hapi.fhir.org/baseR4/Patient'

Query String:

For GET requests, the URL may also contain any necessary query parameters like the id of the patient you are searching for.

When using net.http.get{}, the parameters argument takes in a table of key-value pairs and automatically formats the query string. The url can also be hardcoded to handle query parameters if desired.

The ? indicates the end of the url and beginning of the parameters. Key-value pairs are separated by &.

http://hapi.fhir.org/baseR4/Patient?id=12324&name=Bruce

3) Header - the metadata providing information about the request

The header includes metadata requirements defined by the API to provide information about the request.

headers= {
  ['Content-Type'] = 'application/fhir+json',
  ['Authorization'] = 'Bearer '..token
}

This can contain information such as:

Connection and content types
Authentication information like credentials, cookies, or an access token
MIME types
Entity tags (ETAGS)

4) Body - the payload of the request, containing the content to be sent

Some requests require a body where we add the resource content or additional information to be sent to the server. The HTTP formats will typically be specified by the API you’re working with and often requires the appropriate Content-Type header. Common formats include:

JSON

[{
    "patientid": "33751",
    "status": "active",
    "firstname": ”Bruce",
    "lastname": ”Wayne",
	...
}]

See Parsing and Serializing JSON.

XML

<patient>
  <patientid>33751</patientid>
   <status>active</status>
   <firstname>Bruce</firstname>
   <lastname>Wayne</lastname>
</patient>

See Working with XML

Form Data

local formData = {
      ["file"] = "@/path/to/file.txt",
      ["name"] = "Bruce Wayne",
      ["email"] = "bruce.wayne@example.com"
   }

Form data for data sent from a web form. Typically handled in Lua using string or table functions, storing data as name-value pairs.