VB.NET

DynamoDB - GetItem

See more Amazon DynamoDB Examples

The GetItem operation returns a set of attributes for the item with the given primary key. If there is no matching item, GetItem does not return any data and there will be no Item element in the response. 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.GetItem" \
'   -d '{
'     "TableName": "Thread",
'     "Key": {
'         "ForumName": {
'             "S": "Amazon DynamoDB"
'         },
'         "Subject": {
'             "S": "How do I update multiple items?"
'         }
'     },
'     "ProjectionExpression":"LastPostDateTime, Message, Tags",
'     "ConsistentRead": true,
'     "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": "Thread",
'   "Key": {
'     "ForumName": {
'       "S": "Amazon DynamoDB"
'     },
'     "Subject": {
'       "S": "How do I update multiple items?"
'     }
'   },
'   "ProjectionExpression": "LastPostDateTime, Message, Tags",
'   "ConsistentRead": true,
'   "ReturnConsumedCapacity": "TOTAL"
' }

Dim json As New Chilkat.JsonObject
json.UpdateString("TableName","Thread")
json.UpdateString("Key.ForumName.S","Amazon DynamoDB")
json.UpdateString("Key.Subject.S","How do I update multiple items?")
json.UpdateString("ProjectionExpression","LastPostDateTime, Message, Tags")
json.UpdateBool("ConsistentRead",True)
json.UpdateString("ReturnConsumedCapacity","TOTAL")

rest.AddHeader("Content-Type","application/x-amz-json-1.0")
rest.AddHeader("X-Amz-Target","DynamoDB_20120810.GetItem")
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": "Thread"
'   },
'   "Item": {
'     "Tags": {
'       "SS": [
'         "Update",
'         "Multiple Items",
'         "HelpMe"
'       ]
'     },
'     "LastPostDateTime": {
'       "S": "201303190436"
'     },
'     "Message": {
'       "S": "I want to update multiple items in a single call. What's the best way to do that?"
'     }
'   }
' }

' 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 strVal As String

Dim ConsumedCapacityCapacityUnits As Integer = jsonResponse.IntOf("ConsumedCapacity.CapacityUnits")
Dim ConsumedCapacityTableName As String = jsonResponse.StringOf("ConsumedCapacity.TableName")
Dim ItemLastPostDateTimeS As String = jsonResponse.StringOf("Item.LastPostDateTime.S")
Dim ItemMessageS As String = jsonResponse.StringOf("Item.Message.S")
Dim i As Integer = 0
Dim count_i As Integer = jsonResponse.SizeOfArray("Item.Tags.SS")
While i < count_i
    jsonResponse.I = i
    strVal = jsonResponse.StringOf("Item.Tags.SS[i]")
    i = i + 1
End While