Lua

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). 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.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

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": "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"
-- }

local json = chilkat.JsonObject.new()
json:update_string("TableName", "Thread")
json:update_string("Key.ForumName.S", "Amazon DynamoDB")
json:update_string("Key.Subject.S", "Maximum number of items?")
json:update_string("UpdateExpression", "set LastPostedBy = :val1")
json:update_string("ConditionExpression", "LastPostedBy = :val2")
json:update_string("ExpressionAttributeValues.:val1.S", "alice@example.com")
json:update_string("ExpressionAttributeValues.:val2.S", "fred@example.com")
json:update_string("ReturnValues", "ALL_NEW")

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

-- {
--   "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

local strVal = ""

local AttributesLastPostedByS = jsonResponse:string_of("Attributes.LastPostedBy.S")
local AttributesForumNameS = jsonResponse:string_of("Attributes.ForumName.S")
local AttributesLastPostDateTimeS = jsonResponse:string_of("Attributes.LastPostDateTime.S")
local AttributesSubjectS = jsonResponse:string_of("Attributes.Subject.S")
local AttributesViewsN = jsonResponse:string_of("Attributes.Views.N")
local AttributesMessageS = jsonResponse:string_of("Attributes.Message.S")
local i = 0
local count_i = jsonResponse:size_of_array("Attributes.Tags.SS")
while i < count_i do
    jsonResponse.i = i
    strVal = jsonResponse:string_of("Attributes.Tags.SS[i]")
    i = i + 1
end