Pascal (Lazarus/Delphi)
Pascal (Lazarus/Delphi)
DynamoDB - UpdateItem
See more Amazon DynamoDB Examples
Edits an existing item's attributes, or adds a new item to the table if it does not already exist. You can put, delete, or add attribute values. You can also perform a conditional update on an existing item (insert a new attribute name-value pair if it doesn't exist, or replace an existing name-value pair if it has certain expected attribute values).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;
strVal: string;
AttributesLastPostedByS: string;
AttributesForumNameS: string;
AttributesLastPostDateTimeS: string;
AttributesSubjectS: string;
AttributesViewsN: string;
AttributesMessageS: string;
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.UpdateItem" \
// -d '{
// "TableName": "Thread",
// "Key": {
// "ForumName": {
// "S": "Amazon DynamoDB"
// },
// "Subject": {
// "S": "Maximum number of items?"
// }
// },
// "UpdateExpression": "set LastPostedBy = :val1",
// "ConditionExpression": "LastPostedBy = :val2",
// "ExpressionAttributeValues": {
// ":val1": {"S": "alice@example.com"},
// ":val2": {"S": "fred@example.com"}
// },
// "ReturnValues": "ALL_NEW"
// }'
// 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": "Thread",
// "Key": {
// "ForumName": {
// "S": "Amazon DynamoDB"
// },
// "Subject": {
// "S": "Maximum number of items?"
// }
// },
// "UpdateExpression": "set LastPostedBy = :val1",
// "ConditionExpression": "LastPostedBy = :val2",
// "ExpressionAttributeValues": {
// ":val1": {
// "S": "alice@example.com"
// },
// ":val2": {
// "S": "fred@example.com"
// }
// },
// "ReturnValues": "ALL_NEW"
// }
json := TJsonObject.Create;
json.UpdateString('TableName','Thread');
json.UpdateString('Key.ForumName.S','Amazon DynamoDB');
json.UpdateString('Key.Subject.S','Maximum number of items?');
json.UpdateString('UpdateExpression','set LastPostedBy = :val1');
json.UpdateString('ConditionExpression','LastPostedBy = :val2');
json.UpdateString('ExpressionAttributeValues.:val1.S','alice@example.com');
json.UpdateString('ExpressionAttributeValues.:val2.S','fred@example.com');
json.UpdateString('ReturnValues','ALL_NEW');
rest.AddHeader('Content-Type','application/x-amz-json-1.0');
rest.AddHeader('X-Amz-Target','DynamoDB_20120810.UpdateItem');
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)
// {
// "Attributes": {
// "LastPostedBy": {
// "S": "alice@example.com"
// },
// "ForumName": {
// "S": "Amazon DynamoDB"
// },
// "LastPostDateTime": {
// "S": "20130320010350"
// },
// "Tags": {
// "SS": [
// "Update",
// "Multiple Items",
// "HelpMe"
// ]
// },
// "Subject": {
// "S": "Maximum number of items?"
// },
// "Views": {
// "N": "5"
// },
// "Message": {
// "S": "I want to put 10 million data items to an Amazon DynamoDB table. Is there an upper limit?"
// }
// }
// }
// Sample code for parsing the JSON response...
// Use the following online tool to generate parsing code from sample JSON:
// Generate Parsing Code from JSON
AttributesLastPostedByS := jsonResponse.StringOf('Attributes.LastPostedBy.S');
AttributesForumNameS := jsonResponse.StringOf('Attributes.ForumName.S');
AttributesLastPostDateTimeS := jsonResponse.StringOf('Attributes.LastPostDateTime.S');
AttributesSubjectS := jsonResponse.StringOf('Attributes.Subject.S');
AttributesViewsN := jsonResponse.StringOf('Attributes.Views.N');
AttributesMessageS := jsonResponse.StringOf('Attributes.Message.S');
i := 0;
count_i := jsonResponse.SizeOfArray('Attributes.Tags.SS');
while i < count_i do
begin
jsonResponse.I := i;
strVal := jsonResponse.StringOf('Attributes.Tags.SS[i]');
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.