API endpoint to fetch (GET) words of a user

Part ɪ: Building Serverless Api│Story 07: Creating endpoint to GET words

GIT : Repo | Branch | PR

In the previous part, we added a lambda function to set up an endpoint to our serverless API to add a word to our DynamoDB’s words table.

Next, we would add an endpoint to our API to read words from the words table of logged in user.

Creating a ResponseUtils class

Now that our code is growing, we would like to refactor our code a little to keep it DRY. If you notice, in our lambda functions, code for sending the response for success and error cases is very similar except for the http response status code and the body, thus these two parts of code can be abstracted away in a function with status and body parameterized. So, lets first put this handling response part in a common module and then we will use it in our API functions:

📂 create a sub-folder utils under src

📃 create a file responseUtils.ts under src/utils, 👇:

Adding function to read(get) Word from DynamoDB

• Create a file named getByUser.ts under src/modules/words with below code:👇 (here is the code gist)

Github gist of above file is here

Add the API Endpoint function in serverless.yml

Next, lets configure the API endpoint to map to the above function we added.
In serverless.yml, add a getLoggedUserWords function under functions as shown below:👇

functions:
  createWord:
    handler: src/modules/words/create.main
    events:
      - http:
          path: words
          method: post
          cors: true
          authorizer: aws_iam
  getLoggedUserWords:
    handler: src/modules/words/getByUser.main
    events:
      - http:
          path: words
          method: get
          cors: true
          authorizer: aws_iam

👆 We added a new function getLoggedUserWords.This is similar to the previous endpoint function createWord that we added in the previous part.

events: — http, method:get ⇒ This means the event to trigger this function is http get.
path: words ⇒ The endpoint would have the path /words,
handler: src/modules/words/getByUser.main ⇒ the request would be handled at the main function in the getByUser.ts file (we added above).
cors: true ⇒ enable CORS as the frontend could be on a different domain.
authorier: aws_iam ⇒ this means the access to the API is restricted as per the IAM permissions of the federated identity that the user has been authorized with. We will see how exactly this would work when we would set up an Identity Pool from AWS Cognito service.

Add mock data to test the service locally

From your AWS Console →DynamoDB → tables →vocabWords-dev table → Items, note down the userID of the Item/record that we have posted to the table in the last part when testing the create-word API.

With this userId, set the mock data, create a file named getLoggedUserWords.json under mocks/words with below data:👇

With the mock data ready, let’s test our lambda function:

$ serverless invoke local --function getLoggedUserWords --path     mocks/words/getLoggedUserWords.json --stage dev

👏 Our GET word API using userId is working.

Deploy the service to AWS

npm run devDeploy

That’s it. Next, we would set up endpoint to get a word by its Id.

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