(VB.NET) DynamoDB - UpdateItem

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).

For more information, see https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_UpdateItem.html

Chilkat .NET Downloads Chilkat .NET Framework Chilkat for .NET Core

Dim rest As New Chilkat.Rest
Dim success As Boolean

' 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

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": "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"
' }

Dim json As New Chilkat.JsonObject
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")

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)

' {
'   "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


Dim strVal As String

Dim AttributesLastPostedByS As String = jsonResponse.StringOf("Attributes.LastPostedBy.S")
Dim AttributesForumNameS As String = jsonResponse.StringOf("Attributes.ForumName.S")
Dim AttributesLastPostDateTimeS As String = jsonResponse.StringOf("Attributes.LastPostDateTime.S")
Dim AttributesSubjectS As String = jsonResponse.StringOf("Attributes.Subject.S")
Dim AttributesViewsN As String = jsonResponse.StringOf("Attributes.Views.N")
Dim AttributesMessageS As String = jsonResponse.StringOf("Attributes.Message.S")
Dim i As Integer = 0
Dim count_i As Integer = jsonResponse.SizeOfArray("Attributes.Tags.SS")
While i < count_i
    jsonResponse.I = i
    strVal = jsonResponse.StringOf("Attributes.Tags.SS[i]")
    i = i + 1
End While