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Custom Server

Modern.js encapsulates most server-side capabilities required by projects, typically eliminating the need for server-side development. However, in certain scenarios such as user authentication, request preprocessing, or adding page skeletons, custom server-side logic may still be necessary.

Custom Server Capabilities

Create the server/modern.server.ts file in the project directory, and you can add the following configurations to extend the Server:

  • Middleware
  • Render Middleware
  • Server Plugin

In the Plugin, you can define Middleware and RenderMiddleware. The middleware loading process is illustrated in the following diagram:

Basic Configuration

server/modern.server.ts
import { defineServerConfig } from '@modern-js/server-runtime';

export default defineServerConfig({
  middlewares: [],
  renderMiddlewares: [],
  plugins: [],
});

Type Definition

defineServerConfig type definition is as follows:

import type { MiddlewareHandler } from 'hono';

type MiddlewareOrder = 'pre' | 'post' | 'default';
type MiddlewareObj = {
    name: string;
    path?: string;
    method?: 'options' | 'get' | 'post' | 'put' | 'delete' | 'patch' | 'all';
    handler: MiddlewareHandler | MiddlewareHandler[];
    before?: Array<MiddlewareObj['name']>;
    order?: MiddlewareOrder;
};
type ServerConfig = {
    middlewares?: MiddlewareObj[];
    renderMiddlewares?: MiddlewareObj[];
    plugins?: (ServerPlugin | ServerPluginLegacy)[];
}

Middleware

Middleware supports executing custom logic before and after the request handling and page routing processes in Modern.js services. That is, if custom logic needs to handle both API routes and affect page routes, then Middleware is the obvious choice. If you only need to handle BFF API routes, this can be achieved by configuring the path to the BFF's prefix.

NOTE

In the BFF scenario, BFF routing will only go through Middleware when the runtime framework is Hono.

Using Posture

server/modern.server.ts
import { defineServerConfig, type MiddlewareHandler } from '@modern-js/server-runtime';
import { getMonitors } from '@modern-js/runtime';

export const handler: MiddlewareHandler = async (c, next) => {
  const monitors = getMonitors();
  const start = Date.now();

  await next();

  const end = Date.now();
  // Report Duration
  monitors.timing('request_timing', end - start);
};

export default defineServerConfig({
  middlewares: [
    {
      name: 'request-timing',
      handler,
    },
  ],
});
WARNING

You must execute the next function to proceed with the subsequent Middleware.

RenderMiddleware

If you only need to handle the logic before and after page rendering, modern.js also provides rendering middleware.

Using Posture

server/modern.server.ts
import { defineServerConfig, type MiddlewareHandler } from '@modern-js/server-runtime';

// Inject render performance metrics
const renderTiming: MiddlewareHandler = async (c, next) => {
  const start = Date.now();

  await next();

  const end = Date.now();
  c.res.headers.set('server-timing', `render; dur=${end - start}`);
};

// Modify the Response Body
const modifyResBody: MiddlewareHandler = async (c, next) => {
  await next();

  const { res } = c;
  const text = await res.text();
  const newText = text.replace('<body>', '<body> <h3>bytedance</h3>');

  c.res = c.body(newText, {
    status: res.status,
    headers: res.headers,
  });
};

export default defineServerConfig({
  renderMiddlewares: [
    {
      name: 'render-timing',
      handler: renderTiming,
    },
    {
      name: 'modify-res-body',
      handler: modifyResBody,
    },
  ],
});

Plugin

Modern.js supports adding the aforementioned middleware and rendering middleware for the Server in custom plugins.

Using Posture

server/plugins/server.ts
import type { ServerPluginLegacy } from '@modern-js/server-runtime';

export default (): ServerPluginLegacy => ({
  name: 'serverPlugin',
  setup(api) {
    return {
      prepare(serverConfig) {
        const { middlewares, renderMiddlewares } = api.useAppContext();

        // Inject server-side data for page dataLoader consumption
        middlewares?.push({
          name: 'server-plugin-middleware',
          handler: async (c, next) => {
            c.set('message', 'hi modern.js');
            await next();
            // ...
          },
        });

        // redirect
        renderMiddlewares?.push({
          name: 'server-plugin-render-middleware',
          handler: async (c, next) => {
            const user = getUser(c.req);
            if (!user) {
              return c.redirect('/login');
            }

            await next();
          },
        });
        return serverConfig;
      },
    };
  },
});
server/modern.server.ts
import { defineServerConfig } from '@modern-js/server-runtime';
import serverPlugin from './plugins/serverPlugin';

export default defineServerConfig({
  plugins: [serverPlugin()],
});
src/routes/page.data.ts
import { useHonoContext } from '@modern-js/server-runtime';
import { defer } from '@modern-js/runtime/router';

export default () => {
  const ctx = useHonoContext();
  // Consuming Data Injected by the Server-Side
  const message = ctx.get('message');

  // ...
};
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