Nestjs：在没有类依赖注入的情况下使用 TypeOrm 数据源

Question

I have an unusual request. We are implementing nestjs into our existing express codebase. Before, we were using Typeorm 0.2 and upgraded to 0.3. We are using functions and not classes, therefore, without huge refactoring, we can't use datasource dependency injection. The goal is to use the datasource without the nestjs dependecy injection.

We used to build transactions this way:

import { getManager } from 'typeorm';
    
return getManager().transaction((manager) => {
  // do something
});

Now, with TypeOrm 0.3, getManager is deprecated. The code is compiling and all requests that don't contain the getManager function are working. When the function containing it is called, I get the following error:

ConnectionNotFoundError: Connection "default" was not found.

I tried to work with the datasource directly, but the infamous error of "metadata not found" is coming up and the code does not even compile.

import { getManager } from 'typeorm';

return AppDataSource.transaction((manager) => {
  // do something
});

Entity metadata for BuyerIndustry#companies was not found. Check if you specified a correct entity object and if it's connected in the connection options.

This is, how we set up the datasource and imported it in the AppModule :

import { ConfigService } from '@nestjs/config';
import { DataSource } from 'typeorm';
import { repositories } from './repositories';

const configService = new ConfigService();

export const AppDataSource = new DataSource({
    type: 'postgres',
    host: configService.get('POSTGRES_HOST'),
    port: configService.get('POSTGRES_PORT'),
    username: configService.get('POSTGRES_USER'),
    password: configService.get('POSTGRES_PASSWORD'),
    database: configService.get('POSTGRES_DB'),
    migrations: [__dirname + '/src/database/migrations/*{.ts,.js}'],
    entities: repositories,
    synchronize: false,
});

// repositories.ts
export const repositories = [
    BuyerIndustry,
    Company,
    // and all other entities in the application
];

// typeorm.module.ts
import { Global, Module } from '@nestjs/common';
import { DataSource } from 'typeorm';
import { AppDataSource } from './datasource';

@Global()
@Module({
    imports: [],
    providers: [
        {
            provide: DataSource,
            useFactory: async () => {
                await AppDataSource.initialize();

                return AppDataSource;
            },
        },
    ],
    exports: [DataSource],
})
export class CustomTypeOrmModule {}

// main.module.ts

@Module({
    imports: [
        CustomTypeOrmModule,
        // other modules
    ]
export class AppModule {
    constructor(private dataSource: DataSource) {}
}

Again, I am 100% certain that I imported ALL entities in the repositories.ts . Any idea, how we can use the DataSource directly in functions, without needing a class with the datasource injected? Any help would be appreciated, thanks!

Answer 1

First make sure AppDataSource is initialized. you can do this in the main.ts file

// main.ts
import {AppDataSource } from "..." // Your datasource file

 if (!AppDataSource.isInitialized) {
    await AppDataSource.initialize();
  }

then call it in any service like so

const someRepo = AppDataSource.getRepository(SomeRepoEntity);

someRepo.findOne({where:{id:someId}})