#Cross-Project Invocation

Based on the BFF architecture, Modern.js provides cross-project invocation capabilities, allowing BFF functions created in one project to be invoked by other projects through integrated calls, enabling function sharing and feature reuse across projects. Cross-project invocation consists of producer and consumer sides. The producer is responsible for creating and providing BFF services while generating integrated invocation SDK, and the consumer initiates requests through these SDK.

#BFF Producer

Upgrade Modern.js dependencies to version x.64.4 or higher, then enable cross-project invocation via configuration. Projects with BFF capabilities enabled can act as BFF producers, or you can create standalone BFF applications. When executing dev or build, the following artifacts for consumers will be automatically generated:

• API functions under the dist/client directory
• Runtime configuration functions under the dist/runtime directory
• Interface exports defined in exports field of package.json
• File list for npm publication specified in files field of package.json

#Existing BFF-enabled Projects

1. Enable Cross-Project Invocation

Ensure the current project has BFF enabled with API files defined under api/lambda. Add the following configuration:

export default defineConfig({
  bff: {
    crossProject: true,
  }
});

2. Generate SDK Type Files

To provide type hints for the integrated invocation SDK, enable the declaration option in TypeScript configuration:

"compilerOptions": {
    "declaration": true,
}

#Create BFF Application

1. run @modern-js/create command：

npx @modern-js/create@latest myapi

2. interactive Q & A interface to initialize the project based on the results, with initialization performed according to the default settings:

? Please select the programming language: TS
? Please select the package manager: pnpm

3. Execute the new command，enable BFF:

? Please select the operation you want to perform Enable optional features
? Please select the feature to enable Enable "BFF"
? Please select BFF type Framework mode

4. Execute【Existing BFF-enabled Projects】to turn on the cross-project call switch.

Note: When a project serves solely as a BFF producer, its runtime does not depend on the /src source directory. Removing the /src directory can help optimize the project's build efficiency.

#BFF Consumer

#Intra-Monorepo Invocation

When producer and consumer are in the same Monorepo, directly import the SDK. API functions reside under ${package_name}/api:

import { useState, useEffect } from 'react';
import { get as hello } from '${package_name}/api/hello';

export default () => {
  const [text, setText] = useState('');

  useEffect(() => {
    hello().then(setText);
  }, []);
  return <div>{text}</div>;
};

#Cross-Project Invocation

When producer and consumer are in separate repositories, publish the BFF producer as an npm package. The invocation method remains the same as intra-Monorepo.

#Domain Configuration and Extensions

For real-world scenarios requiring custom BFF service domains, use the configuration function:

import { configure } from '${package_name}/runtime';

configure({
  setDomain() {
    return 'https://your-bff-api.com';
  },
});

The configure function from ${package_name}/runtime supports domain configuration via setDomain, interceptors, and custom SDK. When extending both current project and cross-project SDK on the same page:

import { configure } from '${package_name}/runtime';
import { configure as innerConfigure } from '@modern-js/plugin-bff/client';
import axios from 'axios';

configure({
    setDomain() {
        return 'https://your-bff-api.com';
    },
});

innerConfigure({
  async request(...config: Parameters<typeof fetch>) {
    const [url, params] = config;
    const res = await axios({
      url: url as string,
      method: params?.method as Method,
      data: params?.body,
      headers: {
        'x-header': 'innerConfigure',
      },
    });
    return res.data;
  },
});