What is the role and function of intermediate components in software system architecture?

Middleware components in software system architecture act as an intermediary layer between different parts of an application, providing request and response processing, data flow management, and auxiliary functions.

Main functions of middleware components:

• Processing and modifying incoming requests and outgoing responses (e.g., parsing request body, authentication, logging).
• Managing user sessions and state.
• Ensuring security (access rights verification, filtering).
• Error and exception handling.
• Caching data to improve performance.

In Node.js, for example, middleware is often used in Express.js for sequential processing of HTTP requests:

const express = require('express');
const app = express();

// Middleware for logging
app.use((req, res, next) => {
  console.log(`${req.method} ${req.url}`);
  next();
});

// Middleware for parsing JSON request body
app.use(express.json());

app.get('/', (req, res) => {
  res.send('Hello World');
});

app.listen(3000);

Thus, middleware components help structure the application, divide responsibilities, and simplify support and extension of functionality.