EntityMetadataNotFound：找不到“BusinessApplication”的元数据

Question

我已经使用 TypeORM 一段时间了，没有出现任何问题，但是在进行 API 调用时突然弹出此错误：

EntityMetadataNotFound: No metadata for "BusinessApplication" was found.
    at new EntityMetadataNotFoundError (C:\Users\Robbie\Code\fit-society\node_modules\typeorm\error\EntityMetadataNotFoundError.js:10:28)
    at Connection.getMetadata (C:\Users\Robbie\Code\fit-society\node_modules\typeorm\connection\Connection.js:336:19)
    at EntityManager.<anonymous> (C:\Users\Robbie\Code\fit-society\node_modules\typeorm\entity-manager\EntityManager.js:459:44)
    at step (C:\Users\Robbie\Code\fit-society\node_modules\tslib\tslib.js:136:27)
    at Object.next (C:\Users\Robbie\Code\fit-society\node_modules\tslib\tslib.js:117:57)
    at C:\Users\Robbie\Code\fit-society\node_modules\tslib\tslib.js:110:75
    at new Promise (<anonymous>)
    at Object.__awaiter (C:\Users\Robbie\Code\fit-society\node_modules\tslib\tslib.js:106:16)
    at EntityManager.find (C:\Users\Robbie\Code\fit-society\node_modules\typeorm\entity-manager\EntityManager.js:456:24)
    at module.exports../src/pages/api/business-applications/[id].ts.__webpack_exports__.default.Object (C:\Users\Robbie\Code\fit-society\.next\server\static\development\pages\api\business-applications\[id].js:1648:65)
    at process._tickCallback (internal/process/next_tick.js:68:7)

当调用此代码时会发生这种情况：

EntityMetadataNotFound: No metadata for "BusinessApplication" was found.
    at new EntityMetadataNotFoundError (C:\Users\Robbie\Code\fit-society\node_modules\typeorm\error\EntityMetadataNotFoundError.js:10:28)
    at Connection.getMetadata (C:\Users\Robbie\Code\fit-society\node_modules\typeorm\connection\Connection.js:336:19)
    at EntityManager.<anonymous> (C:\Users\Robbie\Code\fit-society\node_modules\typeorm\entity-manager\EntityManager.js:459:44)
    at step (C:\Users\Robbie\Code\fit-society\node_modules\tslib\tslib.js:136:27)
    at Object.next (C:\Users\Robbie\Code\fit-society\node_modules\tslib\tslib.js:117:57)
    at C:\Users\Robbie\Code\fit-society\node_modules\tslib\tslib.js:110:75
    at new Promise (<anonymous>)
    at Object.__awaiter (C:\Users\Robbie\Code\fit-society\node_modules\tslib\tslib.js:106:16)
    at EntityManager.find (C:\Users\Robbie\Code\fit-society\node_modules\typeorm\entity-manager\EntityManager.js:456:24)
    at module.exports../src/pages/api/business-applications/[id].ts.__webpack_exports__.default.Object (C:\Users\Robbie\Code\fit-society\.next\server\static\development\pages\api\business-applications\[id].js:1648:65)
    at process._tickCallback (internal/process/next_tick.js:68:7)

在 backend/all-entities.ts 中：

import { BusinessApplication } from '../../../backend/all-entities';
import db from '../../../backend/database';

// in a function...
      const manager = await db.getManager();
      // in this case, req.data.id does equal "oldest"
      const application: BusinessApplication | undefined =
      req.data.id === 'oldest'
          ? (await manager.find(BusinessApplication, { order: { dateSubmitted: 'DESC' }, take: 1 }))[0]
          : await manager.findOne(BusinessApplication, { where: { id: parseInt(req.data.id, 10) } });
      if (application == null) throw createError(404, 'Business application not found');
      return application;

在后端/database.ts中：

/**
 * This file exists to solve circular dependency problems with Webpack by explicitly specifying the module loading order.
 * @see https://medium.com/visual-development/how-to-fix-nasty-circular-dependency-issues-once-and-for-all-in-javascript-typescript-a04c987cf0de
 */

import Account_ from './entities/Account';

export { default as Qualification } from './entities/Qualification';

export { default as EditableAccount } from './entities/EditableAccount';
export { default as EditableBusiness } from './entities/EditableBusiness';
export { default as Business } from './entities/Business';
export { default as BusinessApplication, SendableBusinessApplication } from './entities/BusinessApplication';
export { default as EditableCustomer } from './entities/EditableCustomer';
export { default as Customer } from './entities/Customer';

export { default as Offer } from './entities/Offer';
export { default as ProductOffer } from './entities/ProductOffer';
export { default as ServiceOffer } from './entities/ServiceOffer';

在 backend/entities/BusinessApplication.ts 中：

import 'reflect-metadata';
import {
  Connection,
  ConnectionManager,
  ConnectionOptions,
  createConnection,
  EntityManager,
  getConnectionManager
} from 'typeorm';
import { Business, BusinessApplication, Customer, ProductOffer, ServiceOffer, Qualification } from './all-entities';

/**
 * Database manager class
 */
class Database {
  private connectionManager: ConnectionManager;

  constructor() {
    this.connectionManager = getConnectionManager();
  }

  private async getConnection(): Promise<Connection> {
    const CONNECTION_NAME = 'default';
    let connection: Connection;

    if (this.connectionManager.has(CONNECTION_NAME)) {
      connection = this.connectionManager.get(CONNECTION_NAME);
      if (!connection.isConnected) {
        connection = await connection.connect();
      }
    } else {
      const connectionOptions: ConnectionOptions = {
        name: CONNECTION_NAME,
        type: 'postgres',
        url: process.env.DATABASE_URL,
        synchronize: true,
        entities: [Business, BusinessApplication, Qualification, Customer, ProductOffer, ServiceOffer]
      };
      connection = await createConnection(connectionOptions);
    }

    return connection;
  }

  public getManager(): Promise<EntityManager> {
    return this.getConnection().then(conn => conn.manager);
  }
}

const db = new Database();
export default db;

据我所见，导入全部指向正确的文件，我导入了反射元数据，并将@Entity()装饰器放在类上BusinessApplication。那么可能出了什么问题呢？值得注意的是，如果我将await manager.find(BusinessApplication, ...)第一个文件更改为await manager.find('BusinessApplication', ...)它，它可以正常工作，但我不想这样做，因为我会失去智能感知。另外，第一次初始化服务器时不会发生此错误，但在 Webpack 热模块重新加载后，它会中断（这可能在 Next.js 处理页面后或在我更改代码后发生）。

Answer 1

问题

对我来说，这是在 webpack 热重载之后发生的，因为当所有内容都重新加载时，会生成新的实体模型。尽管生成了新的实体模型，但 TypeORM 并不知道它们，因为我只在模块database.ts初始化时与数据库建立了一次连接，正如您从文件中看到的那样。因此，当 TypeORM 比较调用中的新实体manager.find(BusinessApplication, ...)和旧实体时，它表示它们不一样，因为它们不具有引用相等性（JS 中没有两个函数是相同的）。manager.connection.entityMetadatas因此，在与仅包含旧版本的进行比较时，它没有找到元数据。

修复

我只需要在每次重新加载后与数据库建立一个新连接，以便用新的实体元数据填充它。