typescript - EntityMetadataNotFound：找不到 “BusinessApplication” 的任何元資料

我已經使用 TypeORM 一段時間沒有問題，但在發送 API 請求時突然出現這個錯誤：

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)

當這段程式碼被呼叫時就會發生：

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 backend/all-entities.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/database.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;

在 backend/entities/BusinessApplication.ts 中：

import { IsIn, IsString, IsOptional } from 'class-validator';
import { Column, CreateDateColumn, Entity, PrimaryGeneratedColumn } from 'typeorm';
import { EditableBusiness } from '../all-entities';

class PasswordlessBusinessApplication extends EditableBusiness {
  @Column()
  @IsIn(['individual', 'company'])
  type!: 'individual' | 'company';

  @Column({ nullable: true })
  @IsOptional()
  @IsString()
  fein?: string;

  @Column({ nullable: true })
  @IsOptional()
  @IsString()
  professionalCertificationUrl?: string;
}

@Entity()
export default class BusinessApplication extends PasswordlessBusinessApplication {
  @PrimaryGeneratedColumn()
  id!: number;

  @CreateDateColumn()
  dateSubmitted!: Date;

  @Column()
  @IsString()
  passwordHash!: string;
}

/**
 * A business application sent by the client, which contains a password instead of a password hash.
 * Qualification objects do not require id or business.
 */
export class SendableBusinessApplication extends PasswordlessBusinessApplication {
  @IsString()
  password!: string;
}

從我看到的情況來看，所有的匯入都指向正確的檔案，我也匯入了 reflect-metadata，並且在 BusinessApplication 類上加上了 @Entity() 裝飾器。所以可能是哪裡出了問題呢？值得注意的是，如果我將第一個檔案中的 await manager.find(BusinessApplication, ...) 改成 await manager.find('BusinessApplication', ...) 就可以正常運作，但我不想這樣做，因為我會失去智慧提示。此外，這個錯誤在伺服器第一次初始化時不會發生，但在 Webpack 熱模組重載之後就會出錯（這可能發生在 Next.js 處置頁面之後，或者我修改程式碼之後）。

答案＃1

問題

對我來說，這發生在 webpack 熱重載之後，因為當一切被重新加載時，會生成新的實體模型。雖然生成了新的實體模型，但 TypeORM 並不知道它們，因為我只在 database.ts 模組初始化時連接了一次資料庫，如你從檔案中看到的那樣。因此，當 TypeORM 對來自 manager.find(BusinessApplication, ...) 調用的新實體與舊實體進行比較時，它說它們不一樣，因為它們沒有參照相等性（JS 中沒有兩個函數是相同的）。因此，當將其與只包含舊版本的 manager.connection.entityMetadatas 進行比較時，它沒有找到元資料。

修復

我只需要在每次重新加載後建立一個新的資料庫連接，以便它可以填充新的實體元數據。

答案＃2

從你的專案中刪除 dist 資料夾，然後再次執行