middleware-patterns

Middleware Patterns

Built-in Middlewares

The framework provides several built-in middlewares:

Server-Sent Events (SSE)

const { KoaSSEMiddleware } = require("@axiosleo/koapp");

router.any("/sse", async (context) => {
  const func = KoaSSEMiddleware();
  await func(context.koa, async () => {});

  context.koa.sse.send({ data: "hello, world!" });
  context.koa.sse.end();
});

Session Middleware

// Automatically configured when session config is provided
app = new KoaApplication({
  session: {
    maxAge: 1296000000,
    httpOnly: true,
    signed: true,
  },
});

Custom Middleware

Router-Level Middleware

const router = new Router("/api", {
  middlewares: [
    async (context) => {
      // Pre-processing logic
      console.log(`${context.method}: ${context.router.pathinfo}`);
    },
  ],
  afters: [
    async (context) => {
      // Post-processing logic
      console.log(context.response);
    },
  ],
});

Application-Level Middleware

Koa middlewares can be added directly to the Koa instance:

app.koa.use(async (ctx, next) => {
  // Custom middleware logic
  await next();
});

File Upload Middleware

Use @koa/multer for file uploads:

const multer = require("@koa/multer");

router.post("/upload", async (context) => {
  const upload = multer();
  const func = upload.any();
  await func(context.koa, async () => {});

  const file = context.koa.request.files[0];
  // Process file...
});

Middleware Execution Order

1. Application-level Koa middlewares
2. Router middlewares (before handlers)
3. Route handlers
4. Router afters (after handlers)