Create a serverless API that interacts with an AWS DynamoDB table

When we call the API, our request is routed to a Lambda function, which performs the desired action between Lambda and DynamoDB.

**Create a DynamoDB table

• Open the DynamoDB console at https://console.aws.amazon.com/dynamodb/.
• Choose Create table.
• For Table name, enter http-crud-tutorial-items.
• For Partition key, enter id.
• Choose Create table.

Create a Lambda function

• Sign in to the Lambda console at https://console.aws.amazon.com/lambda
• Choose Create function.
• For Function name, enter http-demo-function.
• Under Permissions choose Change default execution role.
• Select Create a new role from AWS policy templates.
• For Role name, enter http-demo-role.

• For Policy templates, choose Simple microservice permissions.

• Create function

• Open the index.mjs under the Code tab, and replace all the code with this sample code.
  

import { DynamoDBClient } from "@aws-sdk/client-dynamodb";
import {
  DynamoDBDocumentClient,
  ScanCommand,
  PutCommand,
  GetCommand,
  DeleteCommand,
} from "@aws-sdk/lib-dynamodb";

const client = new DynamoDBClient({});

const dynamo = DynamoDBDocumentClient.from(client);

const tableName = "items";

export const handler = async (event, context) => {
  let body;
  let statusCode = 200;
  const headers = {
    "Content-Type": "application/json",
  };

  try {
    switch (event.routeKey) {
      case "DELETE /items/{id}":
        await dynamo.send(
          new DeleteCommand({
            TableName: tableName,
            Key: {
              id: event.pathParameters.id,
            },
          })
        );
        body = `Deleted item ${event.pathParameters.id}`;
        break;
      case "GET /items/{id}":
        body = await dynamo.send(
          new GetCommand({
            TableName: tableName,
            Key: {
              id: event.pathParameters.id,
            },
          })
        );
        body = body.Item;
        break;
      case "GET /items":
        body = await dynamo.send(
          new ScanCommand({ TableName: tableName })
        );
        body = body.Items;
        break;
      case "PUT /items":
        let requestJSON = JSON.parse(event.body);
        await dynamo.send(
          new PutCommand({
            TableName: tableName,
            Item: {
              id: requestJSON.id,
              price: requestJSON.price,
              name: requestJSON.name,
            },
          })
        );
        body = `Put item ${requestJSON.id}`;
        break;
      default:
        throw new Error(`Unsupported route: "${event.routeKey}"`);
    }
  } catch (err) {
    statusCode = 400;
    body = err.message;
  } finally {
    body = JSON.stringify(body);
  }

  return {
    statusCode,
    body,
    headers,
  };
};

• Choose Deploy to update the function.

Create an HTTP API

• Sign in to the API Gateway console at https://console.aws.amazon.com/apigateway.
• Choose Create API, and then for HTTP API, choose Build.
• For API name, enter http-demo-api.
• Choose Next.
• Review the stage that API Gateway, choose Next.
• Choose Create.

Create Routes

• Visit https://console.aws.amazon.com/apigateway
• Choose your API.
• Choose Routes.
• Choose Create.
• For Method, choose GET.
• For the path, enter /items/{id}.
• Choose Create.
• Now you need to repeat steps 4-7 for GET /items, DELETE /items/{id}, and PUT /items.

Create Integration
This is used to connect a route to backend resources.

• Visit https://console.aws.amazon.com/apigateway
• Choose your API.
• Choose Integrations.
• Choose Manage integrations, choose create.
• For Integration type, choose Lambda function.
• For Lambda function, enter http-demo-function.
• Choose Create.

Attach our integration to routes

• Visit https://console.aws.amazon.com/apigateway
• Choose your API.
• Choose Integrations.
• Choose a route.
• Under Choose an existing integration, choose the http-demo-function. Choose Attach integration. Repeat these steps 4-6 for all the routes we created earlier.

Testing our API

• Visit https://console.aws.amazon.com/apigateway
• Choose our API

• Take note of the API's invoke URL, and copy it for later.

• Test creating or update an item
  

curl -X "PUT" -H "Content-Type: application/json" -d "{\"id\": \"123\", \"price\": 12345, \"name\": \"myitem\"}" https://abc123.execute-api.us-east-1.amazonaws.com/items

• Test getting ALL items

curl https://abc123.execute-api.us-east-1.amazonaws.com/items

• Test getting an item

curl https://abc123.execute-api.us-east-1.amazonaws.com/items/123

Test deleting an item

curl -X "DELETE" https://abc123.execute-api.us-east-1.amazonaws.com/items/123