Pascal (Lazarus/Delphi)
Pascal (Lazarus/Delphi)
DynamoDB - Query
See more Amazon DynamoDB Examples
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).Chilkat Pascal (Lazarus/Delphi) Downloads
program ChilkatDemo;
// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.
{$IFDEF FPC}
{$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}
uses
{$IFDEF UNIX}
cthreads,
{$ENDIF}
SysUtils,
CkDllLoader,
Chilkat.AuthAws,
Chilkat.Rest,
Chilkat.JsonObject,
Chilkat.StringBuilder;
// ---------------------------------------------------------------------------
procedure RunDemo;
var
success: Boolean;
rest: TRest;
authAws: TAuthAws;
bTls: Boolean;
port: Integer;
bAutoReconnect: Boolean;
json: TJsonObject;
sbRequestBody: TStringBuilder;
sbResponseBody: TStringBuilder;
respStatusCode: Integer;
jsonResponse: TJsonObject;
ReplyDateTimeS: string;
PostedByS: string;
IdS: string;
ConsumedCapacityCapacityUnits: Integer;
ConsumedCapacityTableName: string;
Count: Integer;
ScannedCount: Integer;
i: Integer;
count_i: Integer;
begin
success := False;
rest := TRest.Create;
// 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 := TAuthAws.Create;
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);
// URL: https://dynamodb.us-west-2.amazonaws.com/
bTls := True;
port := 443;
bAutoReconnect := True;
success := rest.Connect('dynamodb.us-west-2.amazonaws.com',port,bTls,bAutoReconnect);
if (success <> True) then
begin
WriteLn('ConnectFailReason: ' + rest.ConnectFailReason);
WriteLn(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 := TJsonObject.Create;
json.UpdateString('TableName','Reply');
json.UpdateString('IndexName','PostedBy-Index');
json.UpdateInt('Limit',3);
json.UpdateBool('ConsistentRead',True);
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 := TStringBuilder.Create;
json.EmitSb(sbRequestBody);
sbResponseBody := TStringBuilder.Create;
success := rest.FullRequestSb('POST','/',sbRequestBody,sbResponseBody);
if (success <> True) then
begin
WriteLn(rest.LastErrorText);
Exit;
end;
respStatusCode := rest.ResponseStatusCode;
WriteLn('response status code = ' + respStatusCode);
if (respStatusCode >= 400) then
begin
WriteLn('Response Status Code = ' + respStatusCode);
WriteLn('Response Header:');
WriteLn(rest.ResponseHeader);
WriteLn('Response Body:');
WriteLn(sbResponseBody.GetAsString());
Exit;
end;
jsonResponse := TJsonObject.Create;
jsonResponse.LoadSb(sbResponseBody);
jsonResponse.EmitCompact := False;
WriteLn(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;
rest.Free;
authAws.Free;
json.Free;
sbRequestBody.Free;
sbResponseBody.Free;
jsonResponse.Free;
end;
// ---------------------------------------------------------------------------
begin
try
RunDemo;
except
on E: Exception do
WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
end;
WriteLn;
{$IFDEF MSWINDOWS}
WriteLn('Press Enter to exit...');
ReadLn;
{$ENDIF}
end.