Middleware Pattern in Fastify

Overview

Chain processing objects to handle requests

Middleware Pattern 1 implementations available

When to Use

When you need to abstract data access logic
When you want to make your code testable
When you need to support multiple data sources
When you want to decouple business logic from infrastructure

Available Implementations

JWT Authentication

JWT middleware with role-based access control

npx hanma add fastify-jwt --framework fastify

JWT verification via @fastify/jwtRole-based access controlToken generation helpers

Basic Example

// Middleware Pattern implementation example
// This shows the basic structure of middleware pattern in Fastify

// Define your interface
interface IRepository {
  findAll(): Promise<T[]>;
  findById(id: string): Promise<T | null>;
  create(data: CreateDto): Promise<T>;
  update(id: string, data: UpdateDto): Promise<T>;
  delete(id: string): Promise<void>;
}

// Implement the pattern
class MiddlewareRepository implements IRepository {
  async findAll(): Promise<T[]> {
    // Implementation
  }

  async findById(id: string): Promise<T | null> {
    // Implementation
  }

  async create(data: CreateDto): Promise<T> {
    // Implementation
  }

  async update(id: string, data: UpdateDto): Promise<T> {
    // Implementation
  }

  async delete(id: string): Promise<void> {
    // Implementation
  }
}

// Use the pattern
const repository = new MiddlewareRepository();
const items = await repository.findAll();

Frequently Asked Questions

What is Middleware Pattern?

Chain processing objects to handle requests. It's a well-established software design pattern that helps organize code for better maintainability and testability.

How does Middleware Pattern work with Fastify?

Fastify provides excellent support for this pattern through its dependency injection system and middleware composition.

What are the benefits?

Improved testability, separation of concerns, easier maintenance, and flexibility to change implementations without affecting business logic.

When should I avoid this pattern?

For very simple applications with minimal logic, the pattern may add unnecessary complexity. Use judgment based on project requirements.