VB.NET

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). VB.NET

Dim success As Boolean = False

Dim rest As New Chilkat.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 New Chilkat.AuthAws
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 Integer = 443
Dim bAutoReconnect As Boolean = True
success = rest.Connect("dynamodb.us-west-2.amazonaws.com",port,bTls,bAutoReconnect)
If (success <> True) Then
    Debug.WriteLine("ConnectFailReason: " & rest.ConnectFailReason)
    Debug.WriteLine(rest.LastErrorText)
    Exit Sub
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 New Chilkat.JsonObject
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 New Chilkat.StringBuilder
json.EmitSb(sbRequestBody)
Dim sbResponseBody As New Chilkat.StringBuilder
success = rest.FullRequestSb("POST","/",sbRequestBody,sbResponseBody)
If (success <> True) Then
    Debug.WriteLine(rest.LastErrorText)
    Exit Sub
End If

Dim respStatusCode As Integer = rest.ResponseStatusCode
Debug.WriteLine("response status code = " & respStatusCode)
If (respStatusCode >= 400) Then
    Debug.WriteLine("Response Status Code = " & respStatusCode)
    Debug.WriteLine("Response Header:")
    Debug.WriteLine(rest.ResponseHeader)
    Debug.WriteLine("Response Body:")
    Debug.WriteLine(sbResponseBody.GetAsString())
    Exit Sub
End If


Dim jsonResponse As New Chilkat.JsonObject
jsonResponse.LoadSb(sbResponseBody)

jsonResponse.EmitCompact = False
Debug.WriteLine(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 Integer = jsonResponse.IntOf("ConsumedCapacity.CapacityUnits")
Dim ConsumedCapacityTableName As String = jsonResponse.StringOf("ConsumedCapacity.TableName")
Dim Count As Integer = jsonResponse.IntOf("Count")
Dim ScannedCount As Integer = jsonResponse.IntOf("ScannedCount")
Dim i As Integer = 0
Dim count_i As Integer = jsonResponse.SizeOfArray("Items")
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
End While