How to Create a File Service
In this document, you’ll learn how to create a file service in the Medusa backend and the methods you must implement in it.
Overview
A file service class is defined in a TypeScript or JavaScript file that’s created in the src/services
directory.
The class must extend the AbstractFileService
class imported from the @medusajs/medusa
package.
Based on services’ naming conventions, the file’s name should be the slug version of the file service’s name
without service
, and the class’s name should be the pascal case of the file service’s name following by Service
.
For example, create the file src/services/local-file.ts
with the following content:
import { AbstractFileService } from "@medusajs/medusa"
import {
DeleteFileType,
FileServiceGetUploadStreamResult,
FileServiceUploadResult,
GetUploadedFileType,
UploadStreamDescriptorType,
} from "@medusajs/types"
class LocalFileService extends AbstractFileService {
async upload(
fileData: Express.Multer.File
): Promise<FileServiceUploadResult> {
throw new Error("Method not implemented.")
}
async uploadProtected(
fileData: Express.Multer.File
): Promise<FileServiceUploadResult> {
throw new Error("Method not implemented.")
}
async delete(fileData: DeleteFileType): Promise<void> {
throw new Error("Method not implemented.")
}
async getUploadStreamDescriptor(
fileData: UploadStreamDescriptorType
): Promise<FileServiceGetUploadStreamResult> {
throw new Error("Method not implemented.")
}
async getDownloadStream(
fileData: GetUploadedFileType
): Promise<NodeJS.ReadableStream> {
throw new Error("Method not implemented.")
}
async getPresignedDownloadUrl(
fileData: GetUploadedFileType
): Promise<string> {
throw new Error("Method not implemented.")
}
}
export default LocalFileService
The examples implement a file service supporting local uploads.
If you’re using TypeScript and you're following along with the implementation, you should install the Multer types package in the root of your Medusa backend to resolve errors within your file service types:
constructor
You can use the constructor
of your file service to access the different services in Medusa through dependency injection.
You can also use the constructor to initialize your integration with the third-party provider. For example, if you use a client to connect to the third-party provider’s APIs, you can initialize it in the constructor and use it in other methods in the service.
Additionally, if you’re creating your file service as an external plugin to be installed on any Medusa backend and you want to access the options added for the plugin, you can access them in the constructor.
Example
// ...
import { Logger } from "@medusajs/medusa"
import * as fs from "fs"
class LocalFileService extends AbstractFileService {
// can also be replaced by an environment variable
// or a plugin option
protected serverUrl = "http://localhost:9000"
protected publicPath = "uploads"
protected protectedPath = "protected-uploads"
protected logger_: Logger
constructor({ logger }: InjectedDependencies) {
// @ts-ignore
super(...arguments)
this.logger_ = logger
// for public uploads
if (!fs.existsSync(this.publicPath)) {
fs.mkdirSync(this.publicPath)
}
// for protected uploads
if (!fs.existsSync(this.protectedPath)) {
fs.mkdirSync(this.protectedPath)
}
}
// ...
}
Parameters
container
Record<string, unknown>RequiredMedusaContainer
that allows you to access other resources, such as services, in your Medusa backend.config
Record<string, unknown>Methods
upload
This method is used to upload a file to the Medusa backend.
Example
class LocalFileService extends AbstractFileService {
// ...
async upload(
fileData: Express.Multer.File
): Promise<FileServiceUploadResult> {
const filePath =
`${this.publicPath}/${fileData.originalname}`
fs.copyFileSync(fileData.path, filePath)
return {
url: `${this.serverUrl}/${filePath}`,
key: filePath,
}
}
// ...
}
This example does not account for duplicate names to maintain simplicity in this guide. So, an uploaded file can replace another existing file that has the same name.
Parameters
fileData
FileRequiredpath
property of the file object.Returns
The details of the upload's result.
uploadProtected
This method is used to upload a file to the Medusa backend, but to a protected storage. Typically, this would be used to store files that shouldn’t be accessible by using the file’s URL or should only be accessible by authenticated users. For example, exported or imported CSV files.
Example
class LocalFileService extends AbstractFileService {
// ...
async uploadProtected(
fileData: Express.Multer.File
): Promise<FileServiceUploadResult> {
const filePath =
`${this.protectedPath}/${fileData.originalname}`
fs.copyFileSync(fileData.path, filePath)
return {
url: `${this.serverUrl}/${filePath}`,
key: filePath
}
}
// ...
}
This example does not account for duplicate names to maintain simplicity in this guide. So, an uploaded file can replace another existing file that has the same name.
Parameters
fileData
FileRequiredpath
property of the file object.Returns
The details of the upload's result.
delete
This method is used to delete a file from storage.
Example
Parameters
The details of the file to remove.
Returns
Promise
Promise<void>RequiredgetUploadStreamDescriptor
This method is used to retrieve a write stream to be used to upload a file.
Example
// ...
import { Stream } from "stream"
class LocalFileService extends AbstractFileService {
// ...
async getUploadStreamDescriptor({
name,
ext,
isPrivate = true,
}: UploadStreamDescriptorType
): Promise<FileServiceGetUploadStreamResult> {
const filePath = `${isPrivate ?
this.publicPath : this.protectedPath
}/${name}.${ext}`
const pass = new Stream.PassThrough()
const writeStream = fs.createWriteStream(filePath)
pass.pipe(writeStream)
return {
writeStream: pass,
promise: Promise.resolve(),
url: `${this.serverUrl}/${filePath}`,
fileKey: filePath,
}
}
// ...
}
Parameters
The details of the file being uploaded.
Returns
The result of the file-stream upload.
getDownloadStream
This method is used to retrieve a read stream for a file, which can then be used to download the file.
Example
class LocalFileService extends AbstractFileService {
async getDownloadStream({
fileKey,
isPrivate = true,
}: GetUploadedFileType
): Promise<NodeJS.ReadableStream> {
const filePath = `${isPrivate ?
this.publicPath : this.protectedPath
}/${fileKey}`
const readStream = fs.createReadStream(filePath)
return readStream
}
// ...
}
Parameters
The details of the file.
Returns
Promise
Promise<ReadableStream>RequiredThe read stream to read and download the file.
Promise
Promise<ReadableStream>RequiredgetPresignedDownloadUrl
This method is used to retrieve a download URL of the file. For some file services, such as S3, a presigned URL indicates a temporary URL to get access to a file.
If your file service doesn’t perform or offer a similar functionality, you can just return the URL to download the file.
Example
class LocalFileService extends AbstractFileService {
async getPresignedDownloadUrl({
fileKey,
isPrivate = true,
}: GetUploadedFileType
): Promise<string> {
// Local upload doesn't provide
// support for presigned URLs,
// so just return the file's URL.
const filePath = `${isPrivate ?
this.publicPath : this.protectedPath
}/${fileKey}`
return `${this.serverUrl}/${filePath}`
}
// ...
}
Parameters
The details of the file.
Returns
Promise
Promise<string>RequiredThe presigned URL to download the file
Promise
Promise<string>RequiredTest Implementation
If you created your file service in a plugin, refer to this guide on how to test plugins.
After finishing your file service implementation:
1. Run the build
command in the root of your Medusa backend:
2. Start the backend with the develop
command:
3. Upload a file using the Admin REST APIs or using the Medusa admin, for example, to upload a product's thumbnail.