fastify-awilix

Dependency injection support for fastify framework, using awilix

Getting started

First install the package and awilix:

npm i fastify-awilix awilix

Next, set up the plugin:

const { fastifyAwilixPlugin } = require('fastify-awilix')
const fastify = require('fastify')

app = fastify({ logger: true })
app.register(fastifyAwilixPlugin, { disposeOnClose: true, disposeOnResponse: true })

Then, register some modules for injection:

const { diContainer } = require('fastify-awilix')
const { asClass, asFunction, Lifetime } = require('awilix')

// Code from the previous example goes here

diContainer.register({
  userRepository: asClass(UserRepository, {
    lifetime: Lifetime.SINGLETON,
    dispose: (module) => module.dispose(),
  }),
})

app.addHook('onRequest', (request, reply, done) => {
  request.diScope.register({
    userService: asFunction(
      ({ userRepository }) => { return new UserService(userRepository, request.params.countryId) }, {
      lifetime: Lifetime.SCOPED,
      dispose: (module) => module.dispose(),
    }),
  })
  done()
})

Note that there is no strict requirement to use classes, it is also possible to register primitive values, using either asFunction(), or asValue(). Check awilix documentation for more details.

After all the modules are registered, they can be resolved with their dependencies injected from app-scoped diContainer and request-scoped diScope. Note that diScope allows resolving all modules from the parent diContainer scope:

app.post('/', async (req, res) => {
  const userRepositoryForReq = req.diScope.resolve('userRepository')
  const userRepositoryForApp = app.diContainer.resolve('userRepository') // This returns exact same result as the previous line
  const userService = req.diScope.resolve('userService')

  // Logic goes here

  res.send({
    status: 'OK',
  })
})

Plugin options

disposeOnClose - automatically invoke configured dispose for app-level diContainer hooks when the fastify instance is closed. Disposal is triggered within onClose fastify hook. Default value is true

disposeOnResponse - automatically invoke configured dispose for request-level diScope hooks after the reply is sent. Disposal is triggered within onResponse fastify hook. Default value is true

Defining classes

All dependency modules are resolved using either the constructor injection (for asClass) or the function argument (for asFunction), by passing the aggregated dependencies object, where keys of the dependencies object match keys used in registering modules:

class UserService {
  constructor({ userRepository }) {
    this.userRepository = userRepository
  }

  dispose() {
    // Disposal logic goes here
  }
}

class UserRepository {
  constructor() {
    // Constructor logic goes here
  }

  dispose() {
    // Disposal logic goes here
  }
}

diContainer.register({
  userService: asClass(UserRepository, {
    lifetime: Lifetime.SINGLETON,
    dispose: (module) => module.dispose(),
  }),
  userRepository: asClass(UserRepository, {
    lifetime: Lifetime.SINGLETON,
    dispose: (module) => module.dispose(),
  }),
})

Typescript usage

By default fastify-awilix is using generic empty Cradle and RequestCradle interfaces, it is possible extend them with your own types:

awilix defines Cradle as a proxy, and calling getters on it will trigger a container.resolve for an according module. Read more

declare module 'fastify-awilix' {
  interface Cradle {
    userService: UserService
  }
  interface RequestCradle {
    user: User
  }
}
//later, type is inferred correctly
fastify.diContainer.cradle.userService
// or
app.diContainer.resolve('userService')
// request scope
request.diScope.resolve('userService')
request.diScope.resolve('user')

Find more in tests or in example from awilix documentation

Using classic injection mode

If you prefer classic injection, you can use it like this:

const { fastifyAwilixPlugin } = require('fastify-awilix/classic')
const fastify = require('fastify')

app = fastify({ logger: true })
app.register(fastifyAwilixPlugin, { disposeOnClose: true, disposeOnResponse: true })

Advanced DI configuration

For more advanced use-cases, check the official awilix documentation