Zig

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. Zig

const std = @import("std");
const chilkat = @import("chilkat");

pub fn main(init: std.process.Init) !void {
    const alloc = init.arena.allocator();

    const rest = try chilkat.Rest.init();
    defer rest.deinit();

    // 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

    const auth_aws = try chilkat.AuthAws.init();
    defer auth_aws.deinit();
    auth_aws.setAccessKey("AWS_ACCESS_KEY");
    auth_aws.setSecretKey("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.)
    auth_aws.setRegion("us-west-2");
    auth_aws.setServiceName("dynamodb");
    // SetAuthAws causes Chilkat to automatically add the following headers: Authorization, X-Amz-Date
    rest.setAuthAws(auth_aws) catch {};

    // URL: https://dynamodb.us-west-2.amazonaws.com/
    const b_tls = true;
    const port = 443;
    const b_auto_reconnect = true;
    rest.connect("dynamodb.us-west-2.amazonaws.com", port, b_tls, b_auto_reconnect) catch {
        std.debug.print("ConnectFailReason: {d}\n", .{rest.getConnectFailReason()});
        std.debug.print("{s}\n", .{try rest.getLastErrorText(alloc)});
        return;
    };

    // 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"
    // }

    const json = try chilkat.JsonObject.init();
    defer json.deinit();
    json.updateString("TableName", "Thread") catch {};
    json.updateString("Key.ForumName.S", "Amazon DynamoDB") catch {};
    json.updateString("Key.Subject.S", "How do I update multiple items?") catch {};
    json.updateString("ProjectionExpression", "LastPostDateTime, Message, Tags") catch {};
    json.updateBool("ConsistentRead", true) catch {};
    json.updateString("ReturnConsumedCapacity", "TOTAL") catch {};

    rest.addHeader("Content-Type", "application/x-amz-json-1.0") catch {};
    rest.addHeader("X-Amz-Target", "DynamoDB_20120810.GetItem") catch {};
    rest.addHeader("Accept-Encoding", "identity") catch {};

    const sb_request_body = try chilkat.StringBuilder.init();
    defer sb_request_body.deinit();
    json.emitSb(sb_request_body) catch {};
    const sb_response_body = try chilkat.StringBuilder.init();
    defer sb_response_body.deinit();
    rest.fullRequestSb("POST", "/", sb_request_body, sb_response_body) catch {
        std.debug.print("{s}\n", .{try rest.getLastErrorText(alloc)});
        return;
    };

    const resp_status_code = rest.getResponseStatusCode();
    std.debug.print("response status code = {d}\n", .{resp_status_code});
    if (resp_status_code >= 400) {
        std.debug.print("Response Status Code = {d}\n", .{resp_status_code});
        std.debug.print("Response Header:\n", .{});
        std.debug.print("{s}\n", .{try rest.getResponseHeader(alloc)});
        std.debug.print("Response Body:\n", .{});
        std.debug.print("{s}\n", .{try sb_response_body.getAsString(alloc)});
        return;
    }

    const json_response = try chilkat.JsonObject.init();
    defer json_response.deinit();
    json_response.loadSb(sb_response_body) catch {};

    json_response.setEmitCompact(false);
    std.debug.print("{s}\n", .{try json_response.emit(alloc)});

    // 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

    var str_val: [:0]const u8 = "";

    _ = json_response.intOf("ConsumedCapacity.CapacityUnits");
    _ = try json_response.stringOf(alloc, "ConsumedCapacity.TableName");
    _ = try json_response.stringOf(alloc, "Item.LastPostDateTime.S");
    _ = try json_response.stringOf(alloc, "Item.Message.S");
    var i: i32 = 0;
    const count_i = json_response.sizeOfArray("Item.Tags.SS");
    while (i < count_i) {
        json_response.setI(i);
        str_val = try json_response.stringOf(alloc, "Item.Tags.SS[i]");
        i = i + 1;
    }
}