(Delphi ActiveX) Creating an application/json HTTP POST Request

Demonstrates how to create an HTTP POST request having the Content-Type application/json, where the body of the HTTP request is the following JSON:

{
   "username" : "my_username",
   "password" : "my_password",
   "validation-factors" : {
      "validationFactors" : [
         {
            "name" : "remote_address",
            "value" : "127.0.0.1"
         }
      ]
   }
}

The generated HTTP request looks like this:

POST /something HTTP/1.1
Content-Type: application/json
Accept: application/json
Host: domain
Content-Length: 216

{
  "username": "my_username",
  "password": "my_password",
  "validation-factors": {
    "validationFactors": [
      {
        "name": "remote_address",
        "value": "127.0.0.1"
      }
    ]
  }
}

Note: This example requires Chilkat v11.1.0 or greater.

Chilkat for Delphi Downloads Chilkat ActiveX DLL for Delphi Chilkat non-ActiveX DLL for Delphi * The examples here use the ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
req: TChilkatHttpRequest;
json: TChilkatJsonObject;
vFactors: TChilkatJsonObject;
vArray: TChilkatJsonArray;
factorObj: TChilkatJsonObject;
requestMime: WideString;

begin
// This example demonstrates building an application/json request.

req := TChilkatHttpRequest.Create(Self);

// The ContentType, HttpVerb, and Path properties should
// always be explicitly set.
req.HttpVerb := 'POST';
req.Path := '/something';
req.ContentType := 'application/json';

// We may wish to add an "Accept" header to the request.
// This tells the server we'll accept an application/json response.
req.AddHeader('Accept','application/json');

// We'll use Chilkat's JSON API to create the JSON body of the HTTP request.
json := TChilkatJsonObject.Create(Self);
json.AppendString('username','my_username');
json.AppendString('password','my_password');

vFactors := TChilkatJsonObject.Create(Self);
json.AppendObject2('validation-factors',vFactors.ControlInterface);

vArray := TChilkatJsonArray.Create(Self);
vFactors.AppendArray2('validationFactors',vArray.ControlInterface);

factorObj := TChilkatJsonObject.Create(Self);
vArray.AddObjectAt2(0,factorObj.ControlInterface);
factorObj.AppendString('name','remote_address');
factorObj.AppendString('value','127.0.0.1');

// Use the JSON for the HTTP request body
// By default, the Emit method will output compact JSON.
// This is best for generating the smallest size request.
// To generate a more human-readable (pretty-printed) JSON request body,
// set the EmitCompact property to FALSE
json.EmitCompact := 0;
req.LoadBodyFromString(json.Emit(),'utf-8');

// View the request that would be sent if HttpSReq was called:
requestMime := req.GenerateRequestText();
Memo1.Lines.Add(requestMime);

// A few important comments about the HTTP request that is generated:
// 
// 1) The Content-Length header is automatically generated based on the actual length of the MIME message
//    that follows the intial (topmost) MIME header.
// 2) The HOST header will automatically get filled in with the actual domain when HttpSReq
//    is called
end;