Create Infrastructure

Update OpenAPI Specification

Update the OpenApi specification to include the loan application scenarios we discussed.

In generateApiSpec function, under components > schemas add the following schemas:

backend/infra/api-definition.ts
LoanApplicationStatus: {
  type: 'string',
  enum: ['APPROVED', 'REJECTED', 'REVIEW'],
},
LoanApplication: {
  type: 'object',
  required: [
    'borrowerEmail',
    'employmentStatus',
    'grossAnnualIncome',
    'monthlyExpenses',
  ],
  properties: {
    borrowerEmail: {
      type: 'string',
    },
    employmentStatus: {
      $ref: '#/components/schemas/EmploymentStatus',
    },
    grossAnnualIncome: {
      type: 'integer',
    },
    monthlyExpenses: {
      type: 'integer',
    },
  },
}

Under paths add the following path:

backend/infra/api-definition.ts
'/loan': {
  post: {
    summary: 'Apply for a loan',
    requestBody: {
      required: true,
      content: {
        'application/json': {
          schema: {
            $ref: '#/components/schemas/LoanApplication',
          },
        },
      },
    },
    description: 'Assesses a borrowers loan application',
    responses: {
      '201': {
        description: 'Loan application created',
        content: {
          'application/json': {
            schema: {
              type: 'object',
              required: ['loanApplicationStatus'],
              properties: {
                loanApplicationStatus: {
                  schema: {
                    $ref: '#/components/schemas/LoanApplicationStatus',
                  },
                },
              },
            },
          },
        },
      },
      '500': {
        description: 'Internal Server Error',
        content: {
          'application/json': {
            schema: {
              type: 'object',
              required: ['message'],
              properties: {
                message: {
                  type: 'string',
                },
              },
            },
          },
        },
      },
    },
    'x-amazon-apigateway-integration': {
      uri: `arn:\${AWS::Partition}:apigateway:\${AWS::Region}:lambda:path/2015-03-31/functions/${applyForLoanHandlerArn}/invocations`,
      responses: {
        default: {
          statusCode: '200',
        },
      },
      passthroughBehavior: 'when_no_match',
      httpMethod: 'POST',
      contentHandling: 'CONVERT_TO_TEXT',
      type: 'aws_proxy',
    },
  },
},

Add an "Apply for Loan" lambda handler

backend/infra/ConfigStack.ts
export function ConfigStack({ stack, app }: StackContext) {
  // ...
  const calculateBorrowingCapacityHandler = new Function(
    stack,
    'calculateBorrowingCapacityLambda',
    {
      handler:
        'src/adaptors/primary/api-gw-calculate-borrowing-capacity.handler',
      functionName: app.logicalPrefixedName('CalculateBorrowingCapacity'),
      bind: [FINANCIAL_DATA_TABLE_NAME],
      permissions: [[financialDataTable.cdk.table, 'grantReadWriteData']],
    }
  );
  const applyForLoanHandler = new Function(stack, 'applyForLoanHandlerLambda', {
    handler: 'src/adaptors/primary/api-gw-apply-for-loan.handler',
    functionName: app.logicalPrefixedName('ApplyForLoan'),
    bind: [FINANCIAL_DATA_TABLE_NAME],
    permissions: [[financialDataTable.cdk.table, 'grantReadWriteData']],
  });
  const createBorrowerProfileHandler = new Function(
  stack,
  'createBorrowerProfileHandlerLambda',
  {
    handler: 'src/adaptors/primary/api-gw-create-borrower-profile.handler',
    functionName: app.logicalPrefixedName('CreateBorrowerProfile'),
    bind: [FINANCIAL_DATA_TABLE_NAME],
    permissions: [[financialDataTable.cdk.table, 'grantReadWriteData']],
  }
);
// ...
}

Add the Lambda Handler parameter to OpenAPI Specification

Update the call to generateApiSpec function to include the applyForLoanHandlerArn:

backend/infra/ConfigStack.ts
// ...
apiDefinition: apigateway.ApiDefinition.fromInline(
  generateApiSpec({
    calculateBorrowingCapacityHandlerArn:
      calculateBorrowingCapacityHandler.functionArn,
    applyForLoanHandlerArn: applyForLoanHandler.functionArn,
    createBorrowerProfileHandlerArn:
      createBorrowerProfileHandler.functionArn,
  })
),
// ...

Grant API Gateway permission to invoke the Apply for Loan lambda

backend/infra/ConfigStack.ts
// ...
  calculateBorrowingCapacityHandler.grantInvoke(
    new iam.ServicePrincipal('apigateway.amazonaws.com', {
      conditions: {
        ArnLike: {
          'aws:SourceArn': api.arnForExecuteApi(
            'GET',
            '/borrowingCapacity',
            api.deploymentStage.stageName
          ),
        },
      },
    })
  );
  applyForLoanHandler.grantInvoke(
    new iam.ServicePrincipal('apigateway.amazonaws.com', {
      conditions: {
        ArnLike: {
          'aws:SourceArn': api.arnForExecuteApi(
            'POST',
            '/loan',
            api.deploymentStage.stageName
          ),
        },
      },
    })
  );
  Config.Parameter.create(stack, {
    API_ENDPOINT: api.url,
  });
  // ...

Deploy your changes

Run the following command:

pnpm run deploy

You should see the following once the deployment is complete:

✔  Building...
 
|  ConfigStack PUBLISH_ASSETS_COMPLETE 
|  ConfigStack applyForLoanHandlerLambda/ServiceRole AWS::IAM::Role CREATE_COMPLETE 
|  ConfigStack applyForLoanHandlerLambda/ServiceRole/DefaultPolicy AWS::IAM::Policy CREATE_COMPLETE 
|  ConfigStack applyForLoanHandlerLambda AWS::Lambda::Function CREATE_COMPLETE 
|  ConfigStack applyForLoanHandlerLambda/Parameter_functionName AWS::SSM::Parameter CREATE_COMPLETE 
|  ConfigStack SourcemapUploader Custom::SourcemapUploader UPDATE_COMPLETE 
|  ConfigStack loanApiGateway AWS::ApiGateway::RestApi UPDATE_COMPLETE 
|  ConfigStack applyForLoanHandlerLambda/LogRetention Custom::LogRetention CREATE_COMPLETE 
|  ConfigStack loanApiGateway/Deployment AWS::ApiGateway::Deployment CREATE_COMPLETE 
|  ConfigStack loanApiGateway/DeploymentStage.prod AWS::ApiGateway::Stage UPDATE_COMPLETE 
|  ConfigStack applyForLoanHandlerLambda AWS::Lambda::Permission CREATE_COMPLETE 
|  ConfigStack calculateBorrowingCapacityLambda AWS::Lambda::Permission CREATE_COMPLETE 
|  ConfigStack createBorrowerProfileHandlerLambda AWS::Lambda::Permission CREATE_COMPLETE 
|  ConfigStack AWS::Lambda::Permission DELETE_COMPLETE 
|  ConfigStack AWS::Lambda::Permission DELETE_COMPLETE 
|  ConfigStack AWS::ApiGateway::Deployment DELETE_COMPLETE 
|  ConfigStack AWS::CloudFormation::Stack UPDATE_COMPLETE 
⠋  Deploying...
 
✔  Deployed:
   ConfigStack
   apiEndpoint: https://xxxxxx.execute-api.ap-southeast-2.amazonaws.com/prod/
   loanApiGatewayEndpointDA311BAB: https://xxxxxx.execute-api.ap-southeast-2.amazonaws.com/prod/

Restart your documentation server

Kill the running documentation server (Ctrl+C) and run the following:

pnpm run docs

Navigate to: http://localhost:3000/hexyback-workshop/docs/hexy/apply-for-a-loan. You'll see the updated API documentation for the Apply for Loan endpoint:

`Apply for Loan` API Endpoint

Create Infrastructure

Update OpenAPI Specification​

Add an "Apply for Loan" lambda handler​

Add the Lambda Handler parameter to OpenAPI Specification​

Grant API Gateway permission to invoke the Apply for Loan lambda​

Deploy your changes​

Restart your documentation server​