NextJS集成MikroORM报错：Cannot use import statement outside a module

问题描述 #

我在 NextJS v14.2.14 项目中集成 MikroORM v6.3.13，仅完成基础配置并编写了一个写入SectionEntity的基础API：

export const dynamic = "force-dynamic";
export async function GET() {
    const orm = await MikroORM.init(config);
    const em = orm.em.fork();

    try {
        const section = new SectionEntity();
        section.locale = "en";
        section.page = "test";
        section.type = "form";
        section.key = "test_section";

        await em.persistAndFlush(section);

        console.log(section.createdAt);
        return NextResponse.json("SUCCESS", { status: 200 });
    } catch (error) {
        return NextResponse.json({ error: `${error}` }, { status: 500 });
    }
}

运行时触发以下错误：

import { Entity, PrimaryKey, Property, ManyToOne, type Rel } from "@mikro-orm/core";

SyntaxError: Cannot use import statement outside a module
    at internalCompileFunction (node:internal/vm:128:18)
    at wrapSafe (node:internal/modules/cjs/loader:1279:20)
    at Module._compile (node:internal/modules/cjs/loader:1331:27)
    at Module._extensions..js (node:internal/modules/cjs/loader:1426:10)
    at Module.load (node:internal/modules/cjs/loader:1205:32)
    at Module._load (node:internal/modules/cjs/loader:1021:12)
    at Module.require (node:internal/modules/cjs/loader:1230:19)
    at mod.require (C:\Projects\mikroorm-basic\node_modules\next\dist\server\require-hook.js:65:28)
    at require (node:internal/modules/helpers:179:18)

执行 npx mikro-orm-esm debug 验证MikroORM CLI配置正常：

Current MikroORM CLI configuration
    - dependencies:
      - mikro-orm 6.3.13
      - node 21.7.1
      - knex 3.1.0
      - pg 8.13.0
      - typescript 5.6.2
    - package.json found
    - ts-node enabled
    - searched config paths:
      - C:/Projects/mikroorm-basic/src/mikro-orm.config.ts (not found)
      - C:/Projects/mikroorm-basic/mikro-orm.config.ts (found)
      - C:/Projects/mikroorm-basic/src/mikro-orm.config.js (not found)
      - C:/Projects/mikroorm-basic/mikro-orm.config.js (not found)
    - configuration found
    - database connection successful
    - will use `entities` array (contains 0 references and 1 paths)
      - C:/Projects/mikroorm-basic/server/entities (found)

实体定义 #

实体文件位于 ./server/entities 目录：

SectionEntity.ts

import { Entity, PrimaryKey, Property, OneToMany, Collection } from "@mikro-orm/core";
import type { SectionType } from "../types/PageContent";
import ContentEntity from "./content.entity";

@Entity()
export default class SectionEntity {
    @PrimaryKey()
    id!: number;

    @Property()
    locale!: string;

    @Property()
    page!: string;

    @Property()
    type!: SectionType;

    @Property()
    key!: string;

    @OneToMany(() => ContentEntity, (content) => content.section)
    contents = new Collection<ContentEntity>(this);

    @Property()
    createdAt: Date = new Date();
}

ContentEntity.ts

import {
    Entity,
    PrimaryKey,
    Property,
    ManyToOne,
    type Rel
} from "@mikro-orm/core";
import type { ContentType } from "../types/PageContent";
import SectionEntity from "./sections.entity";

@Entity()
export default class ContentEntity {
    @PrimaryKey()
    id!: number;

    @ManyToOne({ entity: () => SectionEntity })
    section!: Rel<SectionEntity>;

    @Property()
    type!: ContentType;

    @Property()
    key!: string;

    @Property()
    body!: string;

    @Property()
    createdAt: Date = new Date();
}

项目TS配置 #

尝试过多种旧版本或适配Pages Router的解决方案，均无效；添加 "type": "module" 会导致项目异常。当前 tsconfig.json 配置如下：

{
    "compilerOptions": {
        "target": "ES2022",
        "lib": ["dom", "dom.iterable", "esnext"],
        "allowJs": true,
        "skipLibCheck": true,
        "strict": true,
        "noEmit": true,
        "emitDecoratorMetadata": true,
        "experimentalDecorators": true,
        "esModuleInterop": true,
        "module": "esnext",
        "moduleResolution": "bundler",
        "resolveJsonModule": true,
        "isolatedModules": true,
        "jsx": "preserve",
        "incremental": true,
        "plugins": [
            {
                "name": "next"
            }
        ],
        "paths": {
            "@/*": ["./*"]
        }
    },
    "include": ["next-env.d.ts", "**/*.ts", "**/*.tsx", ".next/types/**/*.ts"],
    "exclude": ["node_modules"]
}

解决方案 #

针对NextJS 14 App Router + MikroORM v6的场景，按以下步骤修复：

1. 配置NextJS转译MikroORM依赖 #

在 next.config.js 中添加 transpilePackages，让NextJS处理MikroORM的ESM模块：

/** @type {import('next').NextConfig} */
const nextConfig = {
  transpilePackages: ['@mikro-orm/core', '@mikro-orm/postgresql', '@mikro-orm/knex'],
}

module.exports = nextConfig;

根据你使用的数据库调整包名，比如MySQL对应 @mikro-orm/mysql

2. 调整MikroORM配置文件 #

修改 mikro-orm.config.ts，启用ESM模式并指定元数据提供者：

import { defineConfig } from '@mikro-orm/postgresql';
import { TsMorphMetadataProvider } from '@mikro-orm/reflection';

export default defineConfig({
  // 替换为你的数据库连接信息
  host: 'localhost',
  port: 5432,
  user: 'your-db-user',
  password: 'your-db-password',
  dbName: 'your-db-name',
  entities: ['./server/entities/**/*.ts'],
  metadataProvider: TsMorphMetadataProvider,
  esm: true,
  tsNode: true,
});

3. 修正API路由代码 #

确保正确导入配置和实体，并且在请求结束后关闭ORM连接：

import { MikroORM } from '@mikro-orm/postgresql';
import config from '../../mikro-orm.config';
import SectionEntity from '../../server/entities/sections.entity';
import { NextResponse } from 'next/server';

export const dynamic = "force-dynamic";
export async function GET() {
    let orm;
    try {
        orm = await MikroORM.init(config);
        const em = orm.em.fork();

        const section = new SectionEntity();
        section.locale = "en";
        section.page = "test";
        section.type = "form";
        section.key = "test_section";

        await em.persistAndFlush(section);

        console.log(section.createdAt);
        return NextResponse.json("SUCCESS", { status: 200 });
    } catch (error) {
        return NextResponse.json({ error: `${error}` }, { status: 500 });
    } finally {
        if (orm) await orm.close(); // 确保连接关闭
    }
}

4. 额外检查 #

• 确保实体文件均为 .ts 扩展名，且在TS配置的 include 范围内
• 不要在 package.json 中添加 "type": "module"，避免与NextJS的模块系统冲突

内容的提问来源于stack exchange，提问作者Paul S.