(Delphi ActiveX) DynamoDB - Query

The Query operation finds items based on primary key values. You can query any table or secondary index that has a composite primary key (a partition key and a sort key).

For more information, see https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_Query.html

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
rest: TChilkatRest;
success: Integer;
authAws: TChilkatAuthAws;
bTls: Integer;
port: Integer;
bAutoReconnect: Integer;
json: TChilkatJsonObject;
sbRequestBody: TChilkatStringBuilder;
sbResponseBody: TChilkatStringBuilder;
respStatusCode: Integer;
jsonResponse: TChilkatJsonObject;
ReplyDateTimeS: WideString;
PostedByS: WideString;
IdS: WideString;
ConsumedCapacityCapacityUnits: Integer;
ConsumedCapacityTableName: WideString;
Count: Integer;
ScannedCount: Integer;
i: Integer;
count_i: Integer;

begin
rest := TChilkatRest.Create(Self);

// Implements the following CURL command:

// curl -X POST https://dynamodb.us-west-2.amazonaws.com/ \
//   -H "Accept-Encoding: identity" \
//   -H "Content-Type: application/x-amz-json-1.0" \
//   -H "Authorization: AWS4-HMAC-SHA256 Credential=<Credential>, SignedHeaders=<Headers>, Signature=<Signature>" \
//   -H "X-Amz-Date: <Date>" \
//   -H "X-Amz-Target: DynamoDB_20120810.Query" \
//   -d '{
//     "TableName": "Reply",
//     "IndexName": "PostedBy-Index",
//     "Limit": 3,
//     "ConsistentRead": true,
//     "ProjectionExpression": "Id, PostedBy, ReplyDateTime",
//     "KeyConditionExpression": "Id = :v1 AND PostedBy BETWEEN :v2a AND :v2b",
//     "ExpressionAttributeValues": {
//         ":v1": {"S": "Amazon DynamoDB#DynamoDB Thread 1"},
//         ":v2a": {"S": "User A"},
//         ":v2b": {"S": "User C"}
//     },
//     "ReturnConsumedCapacity": "TOTAL"
// }'

// Use the following online tool to generate REST code from a CURL command
// Convert a cURL Command to REST Source Code

authAws := TChilkatAuthAws.Create(Self);
authAws.AccessKey := 'AWS_ACCESS_KEY';
authAws.SecretKey := 'AWS_SECRET_KEY';
// Don't forget to change the region to your particular region. (Also make the same change in the call to Connect below.)
authAws.Region := 'us-west-2';
authAws.ServiceName := 'dynamodb';
// SetAuthAws causes Chilkat to automatically add the following headers: Authorization, X-Amz-Date
rest.SetAuthAws(authAws.ControlInterface);

// URL: https://dynamodb.us-west-2.amazonaws.com/
bTls := 1;
port := 443;
bAutoReconnect := 1;
success := rest.Connect('dynamodb.us-west-2.amazonaws.com',port,bTls,bAutoReconnect);
if (success <> 1) then
  begin
    Memo1.Lines.Add('ConnectFailReason: ' + IntToStr(rest.ConnectFailReason));
    Memo1.Lines.Add(rest.LastErrorText);
    Exit;
  end;

// Note: The above code does not need to be repeatedly called for each REST request.
// The rest object can be setup once, and then many requests can be sent.  Chilkat will automatically
// reconnect within a FullRequest* method as needed.  It is only the very first connection that is explicitly
// made via the Connect method.

// Use this online tool to generate code from sample JSON:
// Generate Code to Create JSON

// The following JSON is sent in the request body.

// {
//   "TableName": "Reply",
//   "IndexName": "PostedBy-Index",
//   "Limit": 3,
//   "ConsistentRead": true,
//   "ProjectionExpression": "Id, PostedBy, ReplyDateTime",
//   "KeyConditionExpression": "Id = :v1 AND PostedBy BETWEEN :v2a AND :v2b",
//   "ExpressionAttributeValues": {
//     ":v1": {
//       "S": "Amazon DynamoDB#DynamoDB Thread 1"
//     },
//     ":v2a": {
//       "S": "User A"
//     },
//     ":v2b": {
//       "S": "User C"
//     }
//   },
//   "ReturnConsumedCapacity": "TOTAL"
// }

json := TChilkatJsonObject.Create(Self);
json.UpdateString('TableName','Reply');
json.UpdateString('IndexName','PostedBy-Index');
json.UpdateInt('Limit',3);
json.UpdateBool('ConsistentRead',1);
json.UpdateString('ProjectionExpression','Id, PostedBy, ReplyDateTime');
json.UpdateString('KeyConditionExpression','Id = :v1 AND PostedBy BETWEEN :v2a AND :v2b');
json.UpdateString('ExpressionAttributeValues.:v1.S','Amazon DynamoDB#DynamoDB Thread 1');
json.UpdateString('ExpressionAttributeValues.:v2a.S','User A');
json.UpdateString('ExpressionAttributeValues.:v2b.S','User C');
json.UpdateString('ReturnConsumedCapacity','TOTAL');

rest.AddHeader('Content-Type','application/x-amz-json-1.0');
rest.AddHeader('X-Amz-Target','DynamoDB_20120810.Query');
rest.AddHeader('Accept-Encoding','identity');

sbRequestBody := TChilkatStringBuilder.Create(Self);
json.EmitSb(sbRequestBody.ControlInterface);
sbResponseBody := TChilkatStringBuilder.Create(Self);
success := rest.FullRequestSb('POST','/',sbRequestBody.ControlInterface,sbResponseBody.ControlInterface);
if (success <> 1) then
  begin
    Memo1.Lines.Add(rest.LastErrorText);
    Exit;
  end;
respStatusCode := rest.ResponseStatusCode;
Memo1.Lines.Add('response status code = ' + IntToStr(respStatusCode));
if (respStatusCode >= 400) then
  begin
    Memo1.Lines.Add('Response Status Code = ' + IntToStr(respStatusCode));
    Memo1.Lines.Add('Response Header:');
    Memo1.Lines.Add(rest.ResponseHeader);
    Memo1.Lines.Add('Response Body:');
    Memo1.Lines.Add(sbResponseBody.GetAsString());
    Exit;
  end;

jsonResponse := TChilkatJsonObject.Create(Self);
jsonResponse.LoadSb(sbResponseBody.ControlInterface);

jsonResponse.EmitCompact := 0;
Memo1.Lines.Add(jsonResponse.Emit());

// Sample JSON response:
// (Sample code for parsing the JSON response is shown below)

// {
//   "ConsumedCapacity": {
//     "CapacityUnits": 1,
//     "TableName": "Reply"
//   },
//   "Count": 2,
//   "Items": [
//     {
//       "ReplyDateTime": {
//         "S": "2015-02-18T20:27:36.165Z"
//       },
//       "PostedBy": {
//         "S": "User A"
//       },
//       "Id": {
//         "S": "Amazon DynamoDB#DynamoDB Thread 1"
//       }
//     },
//     {
//       "ReplyDateTime": {
//         "S": "2015-02-25T20:27:36.165Z"
//       },
//       "PostedBy": {
//         "S": "User B"
//       },
//       "Id": {
//         "S": "Amazon DynamoDB#DynamoDB Thread 1"
//       }
//     }
//   ],
//   "ScannedCount": 2
// }

// Sample code for parsing the JSON response...
// Use the following online tool to generate parsing code from sample JSON:
// Generate Parsing Code from JSON

ConsumedCapacityCapacityUnits := jsonResponse.IntOf('ConsumedCapacity.CapacityUnits');
ConsumedCapacityTableName := jsonResponse.StringOf('ConsumedCapacity.TableName');
Count := jsonResponse.IntOf('Count');
ScannedCount := jsonResponse.IntOf('ScannedCount');
i := 0;
count_i := jsonResponse.SizeOfArray('Items');
while i < count_i do
  begin
    jsonResponse.I := i;
    ReplyDateTimeS := jsonResponse.StringOf('Items[i].ReplyDateTime.S');
    PostedByS := jsonResponse.StringOf('Items[i].PostedBy.S');
    IdS := jsonResponse.StringOf('Items[i].Id.S');
    i := i + 1;
  end;
end;