Lua

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. Lua

local chilkat = require("chilkat")

local rest = chilkat.Rest.new()

-- 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

local authAws = chilkat.AuthAws.new()
authAws.access_key = "AWS_ACCESS_KEY"
authAws.secret_key = "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.service_name = "dynamodb"
-- SetAuthAws causes Chilkat to automatically add the following headers: Authorization, X-Amz-Date
rest:set_auth_aws(authAws)

-- URL: https://dynamodb.us-west-2.amazonaws.com/
local bTls = true
local port = 443
local bAutoReconnect = true
local success = rest:connect("dynamodb.us-west-2.amazonaws.com", port, bTls, bAutoReconnect)
if not success then
    print("ConnectFailReason: " .. rest.connect_fail_reason)
    print(rest.last_error_text)
    return
end

-- 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"
-- }

local json = chilkat.JsonObject.new()
json:update_string("TableName", "Thread")
json:update_string("Key.ForumName.S", "Amazon DynamoDB")
json:update_string("Key.Subject.S", "How do I update multiple items?")
json:update_string("ProjectionExpression", "LastPostDateTime, Message, Tags")
json:update_bool("ConsistentRead", true)
json:update_string("ReturnConsumedCapacity", "TOTAL")

rest:add_header("Content-Type", "application/x-amz-json-1.0")
rest:add_header("X-Amz-Target", "DynamoDB_20120810.GetItem")
rest:add_header("Accept-Encoding", "identity")

local sbRequestBody = chilkat.StringBuilder.new()
json:emit_sb(sbRequestBody)
local sbResponseBody = chilkat.StringBuilder.new()
success = rest:full_request_sb("POST", "/", sbRequestBody, sbResponseBody)
if not success then
    print(rest.last_error_text)
    return
end

local respStatusCode = rest.response_status_code
print("response status code = " .. respStatusCode)
if respStatusCode >= 400 then
    print("Response Status Code = " .. respStatusCode)
    print("Response Header:")
    print(rest.response_header)
    print("Response Body:")
    print(sbResponseBody:get_as_string())
    return
end

local jsonResponse = chilkat.JsonObject.new()
jsonResponse:load_sb(sbResponseBody)

jsonResponse.emit_compact = false
print(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

local strVal = ""

local ConsumedCapacityCapacityUnits = jsonResponse:int_of("ConsumedCapacity.CapacityUnits")
local ConsumedCapacityTableName = jsonResponse:string_of("ConsumedCapacity.TableName")
local ItemLastPostDateTimeS = jsonResponse:string_of("Item.LastPostDateTime.S")
local ItemMessageS = jsonResponse:string_of("Item.Message.S")
local i = 0
local count_i = jsonResponse:size_of_array("Item.Tags.SS")
while i < count_i do
    jsonResponse.i = i
    strVal = jsonResponse:string_of("Item.Tags.SS[i]")
    i = i + 1
end