B4X

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. 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.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 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": "How do I update multiple items?"
'      }
'    },
'    "ProjectionExpression": "LastPostDateTime, Message, Tags",
'    "ConsistentRead": true,
'    "ReturnConsumedCapacity": "TOTAL"
'  }

Dim json As ChilkatJsonObject
json.Initialize
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 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)

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