B4X

DynamoDB - UpdateItem

See more Amazon DynamoDB Examples

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). 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.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 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": "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 ChilkatJsonObject
json.Initialize
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 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)

'  {
'    "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 Int = 0
Dim count_i As Int = jsonResponse.SizeOfArray("Attributes.Tags.SS")
Do While i < count_i
    jsonResponse.I = i
    strVal = jsonResponse.StringOf("Attributes.Tags.SS[i]")
    i = i + 1
Loop