Dart

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). 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.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

  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": "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"
  // }

  final json = CkJsonObject();
  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');

  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)

  // {
  //   "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

  var replyDateTimeS = '';
  var postedByS = '';
  var idS = '';

  final consumedCapacityCapacityUnits = jsonResponse.intOf('ConsumedCapacity.CapacityUnits');
  final consumedCapacityTableName = jsonResponse.stringOf('ConsumedCapacity.TableName');
  final count = jsonResponse.intOf('Count');
  final scannedCount = jsonResponse.intOf('ScannedCount');
  var i = 0;
  final countI = jsonResponse.sizeOfArray('Items');
  while (i < countI) {
    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++;
  }
}