@mikro-orm/nestjs 5.2.3 on npm

Based on dario1985/nestjs-mikro-orm.

Description

🚀 Quick Start

First install the module via yarn or npm and do not forget to install the database driver as well:

$ yarn add @mikro-orm/core @mikro-orm/nestjs @mikro-orm/mongodb     # for mongo
$ yarn add @mikro-orm/core @mikro-orm/nestjs @mikro-orm/mysql       # for mysql/mariadb
$ yarn add @mikro-orm/core @mikro-orm/nestjs @mikro-orm/mariadb     # for mysql/mariadb
$ yarn add @mikro-orm/core @mikro-orm/nestjs @mikro-orm/postgresql  # for postgresql
$ yarn add @mikro-orm/core @mikro-orm/nestjs @mikro-orm/sqlite      # for sqlite

$ npm i -s @mikro-orm/core @mikro-orm/nestjs @mikro-orm/mongodb     # for mongo
$ npm i -s @mikro-orm/core @mikro-orm/nestjs @mikro-orm/mysql       # for mysql/mariadb
$ npm i -s @mikro-orm/core @mikro-orm/nestjs @mikro-orm/mariadb     # for mysql/mariadb
$ npm i -s @mikro-orm/core @mikro-orm/nestjs @mikro-orm/postgresql  # for postgresql
$ npm i -s @mikro-orm/core @mikro-orm/nestjs @mikro-orm/sqlite      # for sqlite

Once the installation process is completed, we can import the MikroOrmModule into the root AppModule.

@Module({
  imports: [
    MikroOrmModule.forRoot({
      entities: ['../dist/entities'],
      entitiesTs: ['../src/entities'],
      dbName: 'my-db-name.sqlite3',
      type: 'sqlite',
      baseDir: __dirname,
    }),
  ],
  controllers: [AppController],
  providers: [AppService],
})
export class AppModule {}

The forRoot() method accepts the same configuration object as init() from the MikroORM package. You can also omit the parameter to use the CLI config.

Afterward, the EntityManager will be available to inject across entire project (without importing any module elsewhere).

@Injectable()
export class MyService {

  constructor(private readonly orm: MikroORM,
              private readonly em: EntityManager) { }

}

To define which repositories shall be registered in the current scope you can use the forFeature() method. For example, in this way:

You should not register your base entities via forFeature(), as there are no repositories for those. On the other hand, base entities need to be part of the list in forRoot() (or in the ORM config in general).

// photo.module.ts

@Module({
  imports: [MikroOrmModule.forFeature([Photo])],
  providers: [PhotoService],
  controllers: [PhotoController],
})
export class PhotoModule {}

and import it into the root AppModule:

// app.module.ts
@Module({
  imports: [MikroOrmModule.forRoot(...), PhotoModule],
})
export class AppModule {}

In this way we can inject the PhotoRepository to the PhotoService using the @InjectRepository() decorator:

@Injectable()
export class PhotoService {
  constructor(
    @InjectRepository(Photo)
    private readonly photoRepository: EntityRepository<Photo>
  ) {}

  // ...

}

Auto entities automatically

Manually adding entities to the entities array of the connection options can be tedious. In addition, referencing entities from the root module breaks application domain boundaries and causes leaking implementation details to other parts of the application. To solve this issue, static glob paths can be used.

Note, however, that glob paths are not supported by webpack, so if you are building your application within a monorepo, you won't be able to use them. To address this issue, an alternative solution is provided. To automatically load entities, set the autoLoadEntities property of the configuration object (passed into the forRoot() method) to true, as shown below:

@Module({
  imports: [
    MikroOrmModule.forRoot({
      ...
      autoLoadEntities: true,
    }),
  ],
})
export class AppModule {}

With that option specified, every entity registered through the forFeature() method will be automatically added to the entities array of the configuration object.

Note that entities that aren't registered through the forFeature() method, but are only referenced from the entity (via a relationship), won't be included by way of the autoLoadEntities setting.

Using autoLoadEntities also has no effect on the MikroORM CLI - for that we still need CLI config with the full list of entities. On the other hand, we can use globs there, as the CLI won't go thru webpack.

Request scoped handlers in queues

As mentioned in the docs, we need a clean state for each request. That is handled automatically thanks to the RequestContext helper registered via middleware.

But middlewares are executed only for regular HTTP request handles, what if we need a request scoped method outside of that? One example of that is queue handlers or scheduled tasks.

We can use the @UseRequestContext() decorator. It requires you to first inject the MikroORM instance to current context, it will be then used to create the context for you. Under the hood, the decorator will register new request context for your method and execute it inside the context.

@Injectable()
export class MyService {

  constructor(private readonly orm: MikroORM) { }

  @UseRequestContext()
  async doSomething() {
    // this will be executed in a separate context
  }

}

Serialization caveat

NestJS built-in serialization relies on class-transformer. Since MikroORM wraps every single entity relation in a Reference or a Collection instance (for type-safety), this will make the built-in ClassSerializerInterceptor blind to any wrapped relations. In other words, if you return MikroORM entities from your HTTP or WebSocket handlers, all of their relations will NOT be serialized.

Luckily, MikroORM provides a serialization API which can be used in lieu of ClassSerializerInterceptor.

@Entity()
export class Book {

  @Property({ hidden: true })   // --> Equivalent of class-transformer's `@Exclude`
  hiddenField: number = Date.now();
  
  @Property({ persist: false }) // --> Will only exist in memory (and will be serialized). Similar to class-transformer's `@Expose()`
  count?: number;
  
  @ManyToOne({ serializer: value => value.name, serializedName: 'authorName' })   // Equivalent of class-transformer's `@Transform()`
  author: Author;

}

Using `AsyncLocalStorage` for request context

Since v5 AsyncLocalStorage is used inside RequestContext helper so this section is no longer valid.

By default, the domain api is used in the RequestContext helper. Since @mikro-orm/core@4.0.3, you can use the new AsyncLocalStorage too, if you are on up to date node version:

// create new (global) storage instance
const storage = new AsyncLocalStorage<EntityManager>();

@Module({
  imports: [
    MikroOrmModule.forRoot({
      // ...
      registerRequestContext: false, // disable automatatic middleware
      context: () => storage.getStore(), // use our AsyncLocalStorage instance
    }),
  ],
  controllers: [AppController],
  providers: [AppService],
})
export class AppModule {}

// register the request context middleware
const app = await NestFactory.create(AppModule, { ... });

app.use((req, res, next) => {
  storage.run(orm.em.fork(true, true), next);
});

Using NestJS `Injection Scopes` for request context

Since @nestjs/common@6, you can use the new Injection Scopes (https://docs.nestjs.com/fundamentals/injection-scopes) too:

import { Scope } from '@nestjs/common';

@Module({
  imports: [
    MikroOrmModule.forRoot({
      // ...
      registerRequestContext: false, // disable automatatic middleware
      scope: Scope.REQUEST
    }),
  ],
  controllers: [AppController],
  providers: [AppService]
})
export class AppModule {}

Or, if you're using the Async provider:

import { Scope } from '@nestjs/common';

@Module({
  imports: [
    MikroOrmModule.forRootAsync({
      // ...
      useFactory: () => ({
        // ...
        registerRequestContext: false, // disable automatatic middleware
      }),
      scope: Scope.REQUEST
    })
  ],
  controllers: [AppController],
  providers: [AppService]
})
export class AppModule {}

Please note that this might have some impact on performance, see: https://docs.nestjs.com/fundamentals/injection-scopes#performance

Using custom repositories

When using custom repositories, we can get around the need for @InjectRepository() decorator by naming our repositories the same way as getRepositoryToken() method do:

export const getRepositoryToken = <T> (entity: EntityName<T>) => `${Utils.className(entity)}Repository`;

In other words, as long as we name the repository same was as the entity is called, appending Repository suffix, the repository will be registered automatically in the Nest.js DI container.

**./author.entity.ts**

@Entity({ customRepository: () => AuthorRepository })
export class Author {

  // to allow inference in `em.getRepository()`
  [EntityRepositoryType]?: AuthorRepository;

}

**./author.repository.ts**

export class AuthorRepository extends EntityRepository<Author> {

  // your custom methods...

}

As the custom repository name is the same as what getRepositoryToken() would return, we do not need the @InjectRepository() decorator anymore:

@Injectable()
export class MyService {

  constructor(private readonly repo: AuthorRepository) { }

}

App shutdown and cleanup

By default, NestJS does not listen for system process termination signals (for example SIGTERM). Because of this, the MikroORM shutdown logic will never executed if the process is terminated, which could lead to database connections remaining open and consuming resources. To enable this, the enableShutdownHooks function needs to be called when starting up the application.

async function bootstrap() {
  const app = await NestFactory.create(AppModule);

  // Starts listening for shutdown hooks
  app.enableShutdownHooks();

  await app.listen(3000);
}

More information about enableShutdownHooks

Multiple Database Connections

You can define multiple database connections by registering multiple MikroOrmModule and setting their contextName. If you want to use middleware request context you must disable automatic middleware and register MikroOrmModule with forMiddleware() or use NestJS Injection Scope

@Module({
  imports: [
    MikroOrmModule.forRoot({
      contextName: 'db1',
      registerRequestContext: false, // disable automatatic middleware
      ...
    }),
    MikroOrmModule.forRoot({
      contextName: 'db2',
      registerRequestContext: false, // disable automatatic middleware
      ...
    }),
    MikroOrmModule.forMiddleware()
  ],
  controllers: [AppController],
  providers: [AppService],
})
export class AppModule {}

To access different MikroORM/EntityManager connections you have to use the new injection tokens @InjectMikroORM()/@InjectEntityManager() where you are required to pass the contextName in:

@Injectable()
export class MyService {

  constructor(@InjectMikroORM('db1') private readonly orm1: MikroORM,
              @InjectMikroORM('db2') private readonly orm2: MikroORM,
              @InjectEntityManager('db1') private readonly em1: EntityManager,
              @InjectEntityManager('db2') private readonly em2: EntityManager) { }

}

When defining your repositories with forFeature() method you will need to set which contextName you want it registered against:

// photo.module.ts

@Module({
  imports: [MikroOrmModule.forFeature([Photo], 'db1')],
  providers: [PhotoService],
  controllers: [PhotoController],
})
export class PhotoModule {}

When using the @InjectRepository decorator you will also need to pass the contextName you want to get it from:

@Injectable()
export class PhotoService {
  constructor(
    @InjectRepository(Photo, 'db1')
    private readonly photoRepository: EntityRepository<Photo>
  ) {}

  // ...

}

Testing

The nestjs-mikro-orm package exposes getRepositoryToken() function that returns prepared token based on a given entity to allow mocking the repository.

@Module({
  providers: [
    PhotoService,
    {
      provide: getRepositoryToken(Photo),
      useValue: mockedRepository,
    },
  ],
})
export class PhotoModule {}