Arhitektura modernih web aplikacija – Deo 3: Backend arhitektura: REST, GraphQL i gRPC

GET    /api/users        → lista korisnika
GET    /api/users/123    → jedan korisnik
POST   /api/users        → kreiraj korisnika
PUT    /api/users/123    → ažuriraj korisnika
DELETE /api/users/123    → obriši korisnika

// routes/users.ts
import express from 'express';
const router = express.Router();

interface User {
  id: number;
  name: string;
  email: string;
}

let users: User[] = [
  { id: 1, name: 'Ana', email: 'ana@primer.rs' }
];

// GET /api/users
router.get('/', (req, res) => {
  res.json({
    data: users,
    links: {
      self: '/api/users',
      create: '/api/users'
    }
  });
});

// GET /api/users/1
router.get('/:id', (req, res) => {
  const user = users.find(u => u.id === +req.params.id);
  if (!user) return res.status(404).json({ error: 'Not found' });
  
  res.json({
    data: user,
    links: { self: `/api/users/${user.id}` }
  });
});

export default router;

# Umesto 3 REST poziva:
GET /users
GET /users/1/posts
GET /posts/5/comments

# Jedan GraphQL:
{
  user(id: 1) {
    name
    posts {
      title
      comments {
        text
        author { name }
      }
    }
  }
}

// server.ts
import { ApolloServer } from '@apollo/server';
import { expressMiddleware } from '@apollo/server/express4';
import express from 'express';
import { readFileSync } from 'fs';

const typeDefs = readFileSync('./schema.graphql', 'utf-8');

const users = [{ id: 1, name: 'Ana' }];
const posts = [{ id: 1, userId: 1, title: 'GraphQL je super' }];

const resolvers = {
  Query: {
    user: (_: any, { id }: { id: number }) => users.find(u => u.id === id),
    users: () => users
  },
  User: {
    posts: (user: any) => posts.filter(p => p.userId === user.id)
  }
};

const server = new ApolloServer({ typeDefs, resolvers });
await server.start();

const app = express();
app.use('/graphql', expressMiddleware(server));

app.listen(4000, () => console.log('GraphQL na http://localhost:4000/graphql'));

type User {
  id: ID!
  name: String!
  posts: [Post!]
}

type Post {
  id: ID!
  title: String!
}

type Query {
  user(id: ID!): User
  users: [User!]
}

// user.proto
syntax = "proto3";

service UserService {
  rpc GetUser (GetUserRequest) returns (User);
  rpc ListUsers (Empty) returns (UserList);
}

message GetUserRequest {
  int32 id = 1;
}

message User {
  int32 id = 1;
  string name = 2;
  string email = 3;
}

message UserList {
  repeated User users = 1;
}