Cloudomium Middleware

This project is a set of tools for easier serverless development on AWS Lambda.

Middleware Engine for AWS Lambda

The middleware engine CloudomiumLambda provides methods for adding set of functions in front of the handler, as well as the afterwards.

Before / After The Lambda Handler

There are methods called before and after in CloudomiumLambda. These method adds middleware functions to be called right before or right after executing the handler function. Usually, the middlewares which added to be called before the handler are for processing the request. On the other hand, the middlewares which added to be called after the handler are for processing the response.

| Parameter | Type | Required | Description | | --------- | ---- | -------- | ----------- | | middleware | function | true | a middleware function that implements Middleware interface | | onError | function | false | a function that implements ErrorHandler interface |

To define the handler function, there is a method called execute

| Parameter | Type | Required | Description | | --------- | ---- | -------- | ----------- | | handler | function | true | a handler function that implements Handler interface | | onError | function | false | a function that implements ErrorHandler interface |

const handler = new CloudomiumLambda()
    .before(await middlewareA())
    .after(await middlewareB())
    .execute(async (event, context) => {
        return { statusCode: 204 }
    })

Built-in Middlewares

There are various built-in middlewares. Also, you can easily build your own middlewares by creating a function that implements Middleware interface.

Authentication

This middleware adds an authentication and authorization layer in front of the Lambda handler function. While the jwt token is for authentication part, check function is for authorization.

| Parameter | Type | Required | Description | | --------- | ---- | -------- | ----------- | | jwt | object | true | jsonwebtoken instance | | jwtOptions | object | false | official options for jsonwebtoken instance | | secret | secret | true | the secret value for signing and verifying tokens | | header | string | false | header key for tokens, default value is authorization | | mustSignIn | boolean | false | flag to determine authentication requirement | | check | function | false | function for validating claims inside the token |

import jwt from 'jsonwebtoken'
import { CloudomiumLambda } from '@cloudomium/middleware'

const handler = new CloudomiumLambda()
    .before(await authMiddleware({ jwt, secret: 'my secret', mustSignedIn: true }), (error, type) => console.error(type, error))
    .execute(async (event, context) => {
        return { statusCode: 204 }
    })

CORS

This middleware adds a simple CORS support to the response. It's better (also cheaper) to solve CORS in front of Lambda, instead of invoking one

| Parameter | Type | Required | Description | | --------- | ---- | -------- | ----------- | | origins | string[] | false | allowed origins. default value is "*" | | headers | string[] | false | allowed headers | | methods | string[] | false | allowed methods | | credentials | boolean | false | flag to allow credentials |

import { CloudomiumLambda } from '@cloudomium/middleware'

const handler = new CloudomiumLambda()
    .before(await corsMiddleware({ origins: ['http://localhost:9000'] }), (error, type) => console.error(type, error))
    .execute(async (event, context) => {
        return { statusCode: 204 }
    })

JSON Body Parser

This middleware adds a support for JSON payload.

| Parameter | Type | Required | Description | | --------- | ---- | -------- | ----------- | | base64 | boolean | false | flag for base64 encoding | | compressed | boolean | false | flag for gzip compression |

import { CloudomiumLambda } from '@cloudomium/middleware'

const handler = new CloudomiumLambda()
    .before(await jsonMiddleware(), (error, type) => console.error(type, error))
    .execute(async (event, context) => {
        return { statusCode: 204 }
    })

HTTP Validator

This middleware adds a validation support for input and / or output data

| Parameter | Type | Required | Description | | --------- | ---- | -------- | ----------- | | body | object | false | ZodError model for body | | queryString | object | false | ZodError model for queryString | | pathParameters | object | false | ZodError model for pathParameters | | headers | object | false | ZodError model for headers | | onError | function | false | Error handling function |

import { CloudomiumLambda } from '@cloudomium/middleware'

const handler = new CloudomiumLambda()
    .before(await validate({ body: z.object({ name: z.string() }) }), (error, type) => console.error(type, error))
    .execute(async (event, context) => {
        return { statusCode: 204 }
    })