Dart

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). Dart

import 'package:chilkat/chilkat.dart';

void main() {
  final rest = CkRest();

  // 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

  final authAws = CkAuthAws();
  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/
  final bTls = true;
  final port = 443;
  final bAutoReconnect = true;
  try {
    rest.connect('dynamodb.us-west-2.amazonaws.com', port, bTls, bAutoReconnect);
  } on ChilkatException catch (e) {
    print('ConnectFailReason: ${rest.connectFailReason}');
    print(e.lastErrorText);
    return;
  }

  // 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"
  // }

  final json = CkJsonObject();
  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');

  final sbRequestBody = CkStringBuilder();
  json.emitSb(sbRequestBody);
  final sbResponseBody = CkStringBuilder();
  try {
    rest.fullRequestSb('POST', '/', sbRequestBody, sbResponseBody);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final respStatusCode = rest.responseStatusCode;
  print('response status code = $respStatusCode');
  if (respStatusCode >= 400) {
    print('Response Status Code = $respStatusCode');
    print('Response Header:');
    print(rest.responseHeader);
    print('Response Body:');
    print(sbResponseBody.getAsString());
    return;
  }

  final jsonResponse = CkJsonObject();
  jsonResponse.loadSb(sbResponseBody);

  jsonResponse.emitCompact = false;
  print(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

  var strVal = '';

  final attributesLastPostedByS = jsonResponse.stringOf('Attributes.LastPostedBy.S');
  final attributesForumNameS = jsonResponse.stringOf('Attributes.ForumName.S');
  final attributesLastPostDateTimeS = jsonResponse.stringOf('Attributes.LastPostDateTime.S');
  final attributesSubjectS = jsonResponse.stringOf('Attributes.Subject.S');
  final attributesViewsN = jsonResponse.stringOf('Attributes.Views.N');
  final attributesMessageS = jsonResponse.stringOf('Attributes.Message.S');
  var i = 0;
  final countI = jsonResponse.sizeOfArray('Attributes.Tags.SS');
  while (i < countI) {
    jsonResponse.i = i;
    strVal = jsonResponse.stringOf('Attributes.Tags.SS[i]');
    i++;
  }
}