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Xbase++

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).

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LOCAL nSuccess
LOCAL oRest
LOCAL oAuthAws
LOCAL nBTls
LOCAL nPort
LOCAL nBAutoReconnect
LOCAL oJson
LOCAL oSbRequestBody
LOCAL oSbResponseBody
LOCAL nRespStatusCode
LOCAL oJsonResponse
LOCAL cStrVal
LOCAL cAttributesLastPostedByS
LOCAL cAttributesForumNameS
LOCAL cAttributesLastPostDateTimeS
LOCAL cAttributesSubjectS
LOCAL cAttributesViewsN
LOCAL cAttributesMessageS
LOCAL i
LOCAL nCount_i

nSuccess := 0

oRest := CreateObject("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.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

oAuthAws := CreateObject("Chilkat.AuthAws")
oAuthAws:AccessKey := "AWS_ACCESS_KEY"
oAuthAws: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.)
oAuthAws:Region := "us-west-2"
oAuthAws:ServiceName := "dynamodb"
//  SetAuthAws causes Chilkat to automatically add the following headers: Authorization, X-Amz-Date
oRest:SetAuthAws(oAuthAws)

//  URL: https://dynamodb.us-west-2.amazonaws.com/
nBTls := 1
nPort := 443
nBAutoReconnect := 1
nSuccess := oRest:Connect("dynamodb.us-west-2.amazonaws.com", nPort, nBTls, nBAutoReconnect)
IF (nSuccess != 1)
    ? "ConnectFailReason: " + Str(oRest:ConnectFailReason)
    ? oRest:LastErrorText
    oRest:destroy()
    oAuthAws:destroy()
    RETURN
ENDIF

//  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"
//  }

oJson := CreateObject("Chilkat.JsonObject")
oJson:UpdateString("TableName", "Thread")
oJson:UpdateString("Key.ForumName.S", "Amazon DynamoDB")
oJson:UpdateString("Key.Subject.S", "Maximum number of items?")
oJson:UpdateString("UpdateExpression", "set LastPostedBy = :val1")
oJson:UpdateString("ConditionExpression", "LastPostedBy = :val2")
oJson:UpdateString("ExpressionAttributeValues.:val1.S", "alice@example.com")
oJson:UpdateString("ExpressionAttributeValues.:val2.S", "fred@example.com")
oJson:UpdateString("ReturnValues", "ALL_NEW")

oRest:AddHeader("Content-Type", "application/x-amz-json-1.0")
oRest:AddHeader("X-Amz-Target", "DynamoDB_20120810.UpdateItem")
oRest:AddHeader("Accept-Encoding", "identity")

oSbRequestBody := CreateObject("Chilkat.StringBuilder")
oJson:EmitSb(oSbRequestBody)
oSbResponseBody := CreateObject("Chilkat.StringBuilder")
nSuccess := oRest:FullRequestSb("POST", "/", oSbRequestBody, oSbResponseBody)
IF (nSuccess != 1)
    ? oRest:LastErrorText
    oRest:destroy()
    oAuthAws:destroy()
    oJson:destroy()
    oSbRequestBody:destroy()
    oSbResponseBody:destroy()
    RETURN
ENDIF

nRespStatusCode := oRest:ResponseStatusCode
? "response status code = " + Str(nRespStatusCode)
IF (nRespStatusCode >= 400)
    ? "Response Status Code = " + Str(nRespStatusCode)
    ? "Response Header:"
    ? oRest:ResponseHeader
    ? "Response Body:"
    ? oSbResponseBody:GetAsString()
    oRest:destroy()
    oAuthAws:destroy()
    oJson:destroy()
    oSbRequestBody:destroy()
    oSbResponseBody:destroy()
    RETURN
ENDIF

oJsonResponse := CreateObject("Chilkat.JsonObject")
oJsonResponse:LoadSb(oSbResponseBody)

oJsonResponse:EmitCompact := 0
? oJsonResponse: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

cAttributesLastPostedByS := oJsonResponse:StringOf("Attributes.LastPostedBy.S")
cAttributesForumNameS := oJsonResponse:StringOf("Attributes.ForumName.S")
cAttributesLastPostDateTimeS := oJsonResponse:StringOf("Attributes.LastPostDateTime.S")
cAttributesSubjectS := oJsonResponse:StringOf("Attributes.Subject.S")
cAttributesViewsN := oJsonResponse:StringOf("Attributes.Views.N")
cAttributesMessageS := oJsonResponse:StringOf("Attributes.Message.S")
i := 0
nCount_i := oJsonResponse:SizeOfArray("Attributes.Tags.SS")
DO WHILE i < nCount_i
    oJsonResponse:I := i
    cStrVal := oJsonResponse:StringOf("Attributes.Tags.SS[i]")
    i := i + 1
ENDDO

oRest:destroy()
oAuthAws:destroy()
oJson:destroy()
oSbRequestBody:destroy()
oSbResponseBody:destroy()
oJsonResponse:destroy()