B4X

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). B4X

Dim success As Boolean = False

Dim rest As ChilkatRest
rest.Initialize("rest")

'  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

Dim authAws As ChilkatAuthAws
authAws.Initialize
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/
Dim bTls As Boolean = True
Dim port As Int = 443
Dim bAutoReconnect As Boolean = True
success = rest.Connect("dynamodb.us-west-2.amazonaws.com", port, bTls, bAutoReconnect)
If success <> True Then
    Log("ConnectFailReason: " & rest.ConnectFailReason)
    Log(rest.LastErrorText)
    Return
End If


'  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"
'  }

Dim json As ChilkatJsonObject
json.Initialize
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")

Dim sbRequestBody As ChilkatStringBuilder
sbRequestBody.Initialize
json.EmitSb(sbRequestBody)
Dim sbResponseBody As ChilkatStringBuilder
sbResponseBody.Initialize
success = rest.FullRequestSb("POST", "/", sbRequestBody, sbResponseBody)
If success <> True Then
    Log(rest.LastErrorText)
    Return
End If

Dim respStatusCode As Int = rest.ResponseStatusCode
Log("response status code = " & respStatusCode)
If respStatusCode >= 400 Then
    Log("Response Status Code = " & respStatusCode)
    Log("Response Header:")
    Log(rest.ResponseHeader)
    Log("Response Body:")
    Log(sbResponseBody.GetAsString)
    Return
End If


Dim jsonResponse As ChilkatJsonObject
jsonResponse.Initialize
jsonResponse.LoadSb(sbResponseBody)

jsonResponse.EmitCompact = False
Log(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

Dim ReplyDateTimeS As String
Dim PostedByS As String
Dim IdS As String

Dim ConsumedCapacityCapacityUnits As Int = jsonResponse.IntOf("ConsumedCapacity.CapacityUnits")
Dim ConsumedCapacityTableName As String = jsonResponse.StringOf("ConsumedCapacity.TableName")
Dim Count As Int = jsonResponse.IntOf("Count")
Dim ScannedCount As Int = jsonResponse.IntOf("ScannedCount")
Dim i As Int = 0
Dim count_i As Int = jsonResponse.SizeOfArray("Items")
Do While i < count_i
    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
Loop