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Xbase++

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).

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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 cReplyDateTimeS
LOCAL cPostedByS
LOCAL cIdS
LOCAL nConsumedCapacityCapacityUnits
LOCAL cConsumedCapacityTableName
LOCAL nCount
LOCAL nScannedCount
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.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

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": "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"
//  }

oJson := CreateObject("Chilkat.JsonObject")
oJson:UpdateString("TableName", "Reply")
oJson:UpdateString("IndexName", "PostedBy-Index")
oJson:UpdateInt("Limit", 3)
oJson:UpdateBool("ConsistentRead", 1)
oJson:UpdateString("ProjectionExpression", "Id, PostedBy, ReplyDateTime")
oJson:UpdateString("KeyConditionExpression", "Id = :v1 AND PostedBy BETWEEN :v2a AND :v2b")
oJson:UpdateString("ExpressionAttributeValues.:v1.S", "Amazon DynamoDB#DynamoDB Thread 1")
oJson:UpdateString("ExpressionAttributeValues.:v2a.S", "User A")
oJson:UpdateString("ExpressionAttributeValues.:v2b.S", "User C")
oJson:UpdateString("ReturnConsumedCapacity", "TOTAL")

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

//  {
//    "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

nConsumedCapacityCapacityUnits := oJsonResponse:IntOf("ConsumedCapacity.CapacityUnits")
cConsumedCapacityTableName := oJsonResponse:StringOf("ConsumedCapacity.TableName")
nCount := oJsonResponse:IntOf("Count")
nScannedCount := oJsonResponse:IntOf("ScannedCount")
i := 0
nCount_i := oJsonResponse:SizeOfArray("Items")
DO WHILE i < nCount_i
    oJsonResponse:I := i
    cReplyDateTimeS := oJsonResponse:StringOf("Items[i].ReplyDateTime.S")
    cPostedByS := oJsonResponse:StringOf("Items[i].PostedBy.S")
    cIdS := oJsonResponse:StringOf("Items[i].Id.S")
    i := i + 1
ENDDO

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