Request validation using serverless framework

This is now supported by Serverless framework, so there is no need to use external plugins.

To enable requests validation one need is to add the following to the serverless.yml:

  HttpHandler:
    handler: src/lambda/http/create.handler
    events:
      - http:
          method: post
          path: items
          request:
            schemas:
              application/json: ${file(models/create-todo-model.json)}

Instead of keeping the file location directly under application/json you can also keep the name of the model after defining it under serverless.yml file's apiGateway section. link to documentation

Kindly note that, as of Feb-2022, serverless-offline plugin is not validating the http.request.schemas in your local. Though they are supporting deprecated version http.request.schema.

To implement request validation using serverless you need to do a couple of things: Include your model/header definitions in your stack, and then tell API gateway to use them for request validation.

You'll need to install the following packages:

• serverless-aws-documentation
• serverless-reqvalidator-plugin

And then you'll need to include them in your serverless.yml:

plugins:
  - serverless-reqvalidator-plugin
  - serverless-aws-documentation

Note: below is only a quick run-down of how to incorporate the packages. Visit the packages' documentation pages for more comprehensive examples...

1. Provide API gateway with a description of your models / headers.

   You can import json schemas for your models, and declare http headers using the serverless-aws-documentation plugin. Here's how you'd add a model to your serverless.yml:

   custom:
     documentation:
       api:
         info:
           version: v0.0.0
           title: Some API title
           description: Some API description
       models:
         - name: SomeLambdaRequest
           contentType: application/json
           schema: ${file(models/SomeLambdaRequest.json)} # reference to your model's json schema file. You can also declare the model inline.
   

   And here's how you'd reference the model in your lambda definition:

   functions:
     someLambda:
       handler: src/someLambda.handler
       events:
         - http:
             # ... snip ...
             documentation:
               summary: some summary
               description: some description
               requestBody:
                 description: some description
               requestModels:
                 application/json: SomeLambdaRequest
   

   You can also declare request headers against your lambda definition like so:

   functions:
     someLambda:
       handler: src/someLambda.handler
       events:
         - http:
             # ... snip ...
             documentation:
               summary: some summary
               description: some description
               requestHeaders:
                 - name: x-some-header
                   description: some header value
                   required: true # true or false
                 - name: x-another-header
                   description: some header value
                   required: false # true or false
   

2. Tell API gateway to actually use the models for validation

   This part makes use of the serverless-reqvalidator-plugin package, and you need to add AWS::ApiGateway::RequestValidator resources to your serverless.yml file. You can specify whether you want to validate request body, request headers, or both.

   resources:
     Resources:
       onlyBody:
         Type: AWS::ApiGateway::RequestValidator
         Properties:
           Name: 'only-body'
           RestApiId:
             Ref: ApiGatewayRestApi
           ValidateRequestBody: true # true or false
           ValidateRequestParameters: false # true or false
   

   And then on individual functions you can make use of the validator like so:

   functions:
     someLambda:
       handler: src/someLambda.handler
       events:
         - http:
             # ... snip ...
             reqValidatorName: onlyBody # reference and use the 'only-body' request validator
   

Put all together your lambda definition would end up looking a little like this:

functions:
  someLambda:
    handler: src/someLambda.handler
    events:
      - http:
          # ... snip ...
          reqValidatorName: onlyBody # reference and use the 'only-body' request validator
          documentation:
            summary: some summary
            description: some description
            requestBody:
              description: some description
            requestModels:
              application/json: SomeLambdaRequest
            requestHeaders:
              - name: x-some-header
                description: some header value
                required: true # true or false
              - name: x-another-header
                description: some header value
                required: false # true or false