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Create Express Endpoint

In this document, you’ll learn how to create express endpoints in Medusa.

Note

Following v1.17.2 of @medusajs/medusa, it's highly recommended to use the API Routes instead. Future versions of Medusa may drop support of Express Endpoints.

Basic Implementation​

To create a new endpoint, start by creating a new file in src/api called index.ts. At its basic format, index.ts should look something like this:

src/api/index.ts
import { Router } from "express"

export default (rootDirectory, options) => {
  const router = Router()

  router.get("/hello", (req, res) => {
    res.json({
      message: "Welcome to My Store!",
    })
  })

  return router
}

This exports a function that returns an Express router. The function receives two parameters:

  • rootDirectory is the absolute path to the root directory that your backend is running from.
  • options is an object that contains the configurations exported from medusa-config.js. If your API route is part of a plugin, then it will contain the plugin's options instead.

Building Files​

Custom endpoints must be transpiled and moved to the dist directory before you can start consuming them. When you run your backend using either the medusa develop or npx medusa develop commands, it watches the files under src for any changes, then triggers the build command and restarts the server.

However, the build isn't triggered when the backend first starts running, and it's never triggered when the medusa start or npx medusa start commands are used.

So, make sure to run the build command before starting the backend:

npm run build

Defining Multiple Routes or Middlewares​

Instead of returning an Express router in the function, you can return an array of routes and middlewares.

For example:

src/api/index.ts
import { Router } from "express"

export default (rootDirectory, options) => {
  const router = Router()

  router.get("/hello", (req, res) => {
    res.json({
      message: "Welcome to My Store!",
    })
  })

  // you can also define the middleware
  // in another file and import it
  const middleware = (res, req, next) => {
    // TODO define global middleware
    console.log("hello from middleware")
    next()
  }

  const anotherRouter = Router()
  anotherRouter.get("/store/*", (req, res, next) => {
    // TODO perform an actions for all store endpoints
    next()
  })

  return [middleware, router, anotherRouter]
}

This allows you to export multiple routers and middlewares from the same file. You can also import the routers, routes, and middlewares from other files, then import them in src/api/index.ts instead of defining them within the same file.

Endpoint Path​

Your endpoint can be under any path you wish.

By Medusa’s conventions:

  • All Storefront REST APIs are prefixed by /store. For example, the /store/products endpoint lets you retrieve the products to display them on your storefront.
  • All Admin REST APIs are prefixed by /admin. For example, the /admin/products endpoint lets you retrieve the products to display them on your Admin.

You can also create endpoints that don't reside under these two prefixes, similar to the hello endpoint in the previous example.

CORS Configuration​

If you’re adding a storefront or admin endpoint and you want to access these endpoints from the storefront or Medusa Admin, you need to pass your endpoints Cross-Origin Resource Origin (CORS) options using the cors package.

First, import the necessary utility functions and types from Medusa's packages with the cors package:

import { 
  getConfigFile, 
  parseCorsOrigins,
} from "medusa-core-utils"
import { 
  ConfigModule, 
} from "@medusajs/medusa/dist/types/global"
import cors from "cors"

Next, in the exported function, retrieve the CORS configurations of your backend using the utility functions you imported:

export default (rootDirectory) => {
  // ...

  const { configModule } = 
    getConfigFile<ConfigModule>(rootDirectory, "medusa-config")
  const { projectConfig } = configModule

  // ....
}

Then, create an object that will hold the CORS configurations. Based on whether it's storefront or admin CORS options, you pass it the respective configuration from projectConfig:

const storeCorsOptions = {
  origin: projectConfig.store_cors.split(","),
  credentials: true,
}

Finally, you can either pass the cors middleware for a specific route, or pass it to the entire router:

adminRouter.options("/admin/hello", cors(adminCorsOptions))
adminRouter.get(
  "/admin/hello",
  cors(adminCorsOptions),
  (req, res) => {
    // ...
  }
)

Parse Request Body Parameters​

If you want to accept request body parameters, you need to pass express middlewares that parse the payload type to your router.

For example:

src/api/index.ts
import bodyParser from "body-parser"
import express, { Router } from "express"


export default (rootDirectory, pluginOptions) => {
  const router = Router()

  router.use(express.json())
  router.use(express.urlencoded({ extended: true }))

  router.post("/store/hello", (req, res) => {
    res.json({
      message: req.body.name,
    })
  })

  return router
}

In the code snippet above, you use the following middlewares:

  • express.json(): parses requests with JSON payloads
  • express.urlencoded(): parses requests with urlencoded payloads.

You can learn about other available middlewares in the Express documentation.

Protected Routes​

Protected routes are routes that should only be accessible by logged-in customers or users.

Protect Store Routes​

There are two approaches to make a storefront route protected:

  • Using the requireCustomerAuthentication middleware, which disallows unauthenticated customers from accessing a route, and allows you to access the logged-in customer's ID.
  • Using the authenticateCustomer middleware, which allows both authenticated and unauthenticated customers to access your route, but allows you to access the logged-in customer's ID as well.

To make a storefront route protected using either middlewares, first, import the middleware at the top of your file:

import { requireCustomerAuthentication } from "@medusajs/medusa"
// import { authenticateCustomer } from "@medusajs/medusa"

Then, pass the middleware to either a single route or an entire router:

// only necessary if you're passing cors options per route
router.options("/store/hello", cors(storeCorsOptions))
router.get(
  "/store/hello",
  cors(storeCorsOptions),
  requireCustomerAuthentication(), 
  // authenticateCustomer()
  async (req, res) => {
    // access current customer
    const id = req.user.customer_id
    // if you're using authenticateCustomer middleware
    // check if id is set first

    const customerService = req.scope.resolve("customerService")
      
    const customer = await customerService.retrieve(id)
    // ...
  }
)

Protect Admin Routes​

To protect admin routes and only allow logged-in users from accessing them, first, import the authenticate middleware at the top of the file:

import { authenticate } from "@medusajs/medusa"

Then, pass the middleware to either a single route or an entire router:

// only necessary if you're passing cors options per route
adminRouter.options("/admin/hello", cors(adminCorsOptions))
adminRouter.get(
  "/admin/hello", 
  cors(adminCorsOptions), 
  authenticate(),
  async (req, res) => {
    // access current user
    const id = req.user.userId
    const userService = req.scope.resolve("userService")
      
    const user = await userService.retrieve(id)
    // ...
  }
)

Retrieve Medusa Config​

As mentioned, the second parameter options includes the configurations exported from medusa-config.js. However, in plugins it only includes the plugin's options.

If you need to access the Medusa configuration in your endpoint, you can use the getConfigFile method imported from medusa-core-utils. It accepts the following parameters:

  1. rootDirectory: The first parameter is a string indicating root directory of your Medusa backend.
  2. config: The second parameter is a string indicating the name of the config file, which should be medusa-config unless you change it.

The function returns an object with the following properties:

  1. configModule: An object containing the configurations exported from medusa-config.js.
  2. configFilePath: A string indicating absolute path to the configuration file.
  3. error: if any errors occur, they'll be included as the value of this property. Otherwise, its value will be undefined.

Here's an example of retrieving the configurations within an endpoint using getConfigFile:

src/api/index.ts
import { Router } from "express"
import { ConfigModule } from "@medusajs/medusa"
import { getConfigFile } from "medusa-core-utils"

export default (rootDirectory) => {
  const router = Router()
  const { configModule } = getConfigFile<ConfigModule>(
    rootDirectory,
    "medusa-config"
  )

  router.get("/store-cors", (req, res) => {
    res.json({
      store_cors: configModule.projectConfig.store_cors,
    })
  })

  return router
}

Notice that getConfigFile is a generic function. So, if you're using TypeScript, you should pass it the type ConfigModule imported from @medusajs/medusa.

If you're accessing custom configurations, you'll need to create a new type that defines these configurations. For example:

src/api/index.ts
import { Router } from "express"
import { ConfigModule } from "@medusajs/medusa"
import { getConfigFile } from "medusa-core-utils"

type MyConfigModule = ConfigModule & {
  projectConfig: {
    custom_config?: string
  }
}

export default (rootDirectory) => {
  const router = Router()
  const { configModule } = getConfigFile<MyConfigModule>(
    rootDirectory,
    "medusa-config"
  )

  router.get("/hello", (req, res) => {
    res.json({
      custom_config: configModule.projectConfig.custom_config,
    })
  })

  return router
}

Handle Errors​

As Medusa uses v4 of Express, you need to manually handle errors thrown asynchronously as explained in Express's documentation.

You can use middlewares to handle errors. You can also use middlewares defined by Medusa, which ensure that your error handling is consistent across your Medusa backend.

Note

Code snippets are taken from the full example available at the end of this document.

To handle errors using Medusa's middlewares, first, import the errorHandler middleware from @medusajs/medusa and apply it on your routers. Make sure it's applied after all other middlewares and routes:

src/api/index.ts
import express, { Router } from "express"
import adminRoutes from "./admin"
import storeRoutes from "./store"
import { errorHandler } from "@medusajs/medusa"

export default (rootDirectory, options) => {
  const router = Router()

  router.use(express.json())
  router.use(express.urlencoded({ extended: true }))

  adminRoutes(router, options)
  storeRoutes(router, options)

  router.use(errorHandler())

  return router
}

Then, wrap the function handler of every route with the wrapHandler middleware imported from @medusajs/medusa. For example:

src/api/admin.ts
import { wrapHandler } from "@medusajs/medusa"

// ...

export default function adminRoutes(
  router: Router,
  options: ConfigModule
) {
  // ...

  adminRouter.get("/posts", wrapHandler(async (req, res) => {
    const postService: PostService = 
      req.scope.resolve("postService")

    res.json({
      posts: await postService.list(),
    })
  }))
  
  // ...
}

Alternatively, you can define the endpoints in different files, and import and use them in your router:

src/api/admin.ts
import { wrapHandler } from "@medusajs/medusa"

// ...

export default function adminRoutes(
  router: Router,
  options: ConfigModule
) {
  // ...
  
  adminRouter.get(
    "/posts",
    wrapHandler(require("./list-posts").default)
  )
  
  // ...
}

Now all errors thrown in your custom endpoints, including in their custom services, will be caught and returned to the user.

However, if you throw errors like this:

throw new Error ("Post was not found")

You'll notice that the endpoint returns the following object error in the response:

{
  "code": "unknown_error",
  "type": "unknown_error",
  "message": "An unknown error occurred."
}

To ensure the error message is relayed in the response, it's recommended to use MedusaError imported from @medusajs/utils as the thrown error instead:

import { MedusaError } from "@medusajs/utils"

// ...

throw new MedusaError(
  MedusaError.Types.NOT_FOUND,
  "Post was not found"
)

The constructor of MedusaError accepts the following parameters:

  1. The first parameter is the type of the error. You can use one of the predefined errors under MedusaError.Types, such as MedusaError.Types.NOT_FOUND which sets the response status code to 404 automatically.
  2. The second parameter is the message of the error.
  3. The third parameter is an optional code, which is a string, that can be returned in the error object.

After using MedusaError, you'll notice that the returned error in the response provides a clearer message:

{
  "type": "not_found",
  "message": "Post was not found"
}

Use Other Resources​

Entities and Repositories​

Your endpoints likely perform an action on an entity. For example, you may create an endpoint to retrieve a list of posts.

You can perform actions on an entity either through its Repository or through a service. This section covers how to retrieve a repository in an endpoint, but it's recommended to use services instead.

You can retrieve any registered resource, including repositories, in your endpoint using req.scope.resolve passing it the resource's registration name in the dependency container. Repositories are registered as their camel-case name. So, for example, if you have a PostRepository, it's registered as postRepository.

Here’s an example of an endpoint that retrieves the list of posts in a store:

Note

Posts are represented by a custom entity not covered in this guide. You can refer to the entities for more details on how to create a custom entity.

import { PostRepository } from "../repositories/post"
import { EntityManager } from "typeorm"

// ...

export default () => {
  // ...

  storeRouter.get("/posts", async (req, res) => {
    const postRepository: typeof PostRepository = 
      req.scope.resolve("postRepository")
    const manager: EntityManager = req.scope.resolve("manager")
    const postRepo = manager.withRepository(postRepository)

    return res.json({
      posts: await postRepo.find(),
    })
  })

  // ...
}

Notice that to retrieve an instance of the repository, you need to retrieve first Typeorm's Entity manager and use its withRepository method.

Services​

Services in Medusa bundle a set of functionalities into one class. Typically, these functionalities are associated with an entity, such as methods to retrieve, create, or update its records.

You can retrieve any registered resource, including services, in your endpoint using req.scope.resolve passing it the service’s registration name in the dependency container. Services are registered as their camel-case name. So, for example, if you have a PostService, it's registered as postService.

Here’s an example of an endpoint that retrieves the list of posts in a store:

Note

PostService is a custom service that is not covered in this guide. You can refer to the services documentation for more details on how to create a custom service, and find an example of PostService

storeRouter.get("/posts", async (req, res) => {
  const postService: PostService = req.scope.resolve(
    "postService"
  )

  return res.json({
    posts: await postService.list(),
  })
})

Other Resources​

Any resource that is registered in the dependency container, such as strategies or file services, can be accessed through req.scope.resolve. Refer to the dependency injection documentation for details on registered resources.

Example: CRUD Endpoints​

This section services as an example of creating endpoints that perform Create, Read, Update, and Delete (CRUD) operations. Note that all admin endpoints are placed in src/api/admin.ts, and store endpoints are placed in src/api/store.ts. You can also place each endpoint in a separate file, import it, and add it to its respective router.

You can refer to the Entities and Services documentation to learn how to create the custom entities and services used in this example.

import express, { Router } from "express"
import adminRoutes from "./admin"
import storeRoutes from "./store"
import { errorHandler } from "@medusajs/medusa"

export default (rootDirectory, options) => {
  const router = Router()

  router.use(express.json())
  router.use(express.urlencoded({ extended: true }))

  adminRoutes(router, options)
  storeRoutes(router, options)

  router.use(errorHandler())

  return router
}

See Also​

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