ultimate-crud/examples/error-handling-demo.js

Ultimate dynamic CRUD API generator with REST, GraphQL, OpenAPI support and association handling for Node.js/Express/Sequelize

/**
 * Error Handling Demo for Ultimate CRUD
 * Demonstrates proper HTTP status codes for database validation errors
 * 
 * @license MIT
 * @copyright 2025 cnos-dev
 * @author Harish Kashyap (CNOS Dev)
 */

const express = require('express');
const { Sequelize } = require('sequelize');
const UltimateCrud = require('../index');

const app = express();
app.use(express.json());

// SQLite database for demo
const sequelize = new Sequelize({
  dialect: 'sqlite',
  storage: 'error-demo.db',
  logging: false
});

// Entity configuration with comprehensive error messages
const entities = [
  {
    name: 'users',
    type: 'table',
    route: '/api/users',
    responseMessages: {
      200: 'Users retrieved successfully',
      201: 'User created successfully',
      400: 'Invalid request data',
      404: 'User not found',
      409: 'User with this email or username already exists',
      422: 'User data validation failed',
      500: 'Internal server error occurred'
    }
  },
  {
    name: 'posts',
    type: 'table',
    route: '/api/posts',
    associations: [
      {
        type: 'belongsTo',
        target: 'users',
        foreignKey: 'authorId',
        as: 'author'
      }
    ],
    responseMessages: {
      200: 'Posts retrieved successfully',
      201: 'Post created successfully',
      404: 'Post not found',
      409: 'Post with this title already exists',
      422: 'Post data validation failed or referenced user does not exist',
      500: 'Server error while processing post'
    }
  }
];

async function setupDatabase() {
  console.log('🔧 Setting up database with constraints...');
  
  try {
    // Create users table with constraints
    await sequelize.query(`
      CREATE TABLE IF NOT EXISTS users (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        username VARCHAR(50) NOT NULL UNIQUE,
        email VARCHAR(100) NOT NULL UNIQUE,
        firstName VARCHAR(50) NOT NULL,
        lastName VARCHAR(50),
        age INTEGER CHECK (age >= 0 AND age <= 150),
        created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
        updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
      )
    `);

    // Create posts table with foreign key constraint
    await sequelize.query(`
      CREATE TABLE IF NOT EXISTS posts (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        title VARCHAR(200) NOT NULL UNIQUE,
        content TEXT NOT NULL,
        author_id INTEGER NOT NULL,
        published BOOLEAN DEFAULT 0,
        created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
        updated_at DATETIME DEFAULT CURRENT_TIMESTAMP,
        FOREIGN KEY (author_id) REFERENCES users(id)
      )
    `);

    console.log('✅ Database tables created with constraints');
  } catch (error) {
    console.error('❌ Database setup failed:', error.message);
    throw error;
  }
}

async function startServer() {
  try {
    // Setup database
    await setupDatabase();

    // Initialize Ultimate CRUD
    const ultimateCrud = UltimateCrud.create({
      app,
      sequelize,
      entities,
      enableGraphQL: false, // Disable for this demo
      enableRest: true,
      enableOpenAPI: true,
      syncDatabase: false // We manually created tables
    });

    await ultimateCrud.initialize();

    const PORT = process.env.PORT || 3000;
    app.listen(PORT, () => {
      console.log(`🚀 Error Handling Demo Server running on http://localhost:${PORT}`);
      console.log(`📋 OpenAPI Spec: http://localhost:${PORT}/openapi.json`);
      
      console.log('\n📖 Error Handling Demo Scenarios:');
      console.log('=====================================');
      
      console.log('\n1️⃣ SUCCESS - Create valid user:');
      console.log(`curl -X POST http://localhost:${PORT}/api/users \\`);
      console.log(`  -H "Content-Type: application/json" \\`);
      console.log(`  -d '{"username":"john_doe","email":"john@example.com","firstName":"John","lastName":"Doe","age":25}'`);
      
      console.log('\n2️⃣ ERROR 409 - Duplicate email/username:');
      console.log(`curl -X POST http://localhost:${PORT}/api/users \\`);
      console.log(`  -H "Content-Type: application/json" \\`);
      console.log(`  -d '{"username":"john_doe","email":"john@example.com","firstName":"Jane","lastName":"Smith","age":30}'`);
      
      console.log('\n3️⃣ ERROR 422 - Validation failure (missing required field):');
      console.log(`curl -X POST http://localhost:${PORT}/api/users \\`);
      console.log(`  -H "Content-Type: application/json" \\`);
      console.log(`  -d '{"username":"jane_doe","email":"jane@example.com","age":25}'`);
      
      console.log('\n4️⃣ ERROR 422 - Invalid data (age constraint):');
      console.log(`curl -X POST http://localhost:${PORT}/api/users \\`);
      console.log(`  -H "Content-Type: application/json" \\`);
      console.log(`  -d '{"username":"invalid_user","email":"invalid@example.com","firstName":"Invalid","age":-5}'`);
      
      console.log('\n5️⃣ ERROR 422 - Foreign key constraint (non-existent user):');
      console.log(`curl -X POST http://localhost:${PORT}/api/posts \\`);
      console.log(`  -H "Content-Type: application/json" \\`);
      console.log(`  -d '{"title":"Test Post","content":"Post content","authorId":999}'`);
      
      console.log('\n6️⃣ SUCCESS - Valid post creation (create user first):');
      console.log(`curl -X POST http://localhost:${PORT}/api/posts \\`);
      console.log(`  -H "Content-Type: application/json" \\`);
      console.log(`  -d '{"title":"My First Post","content":"This is my first post content","authorId":1}'`);
      
      console.log('\n7️⃣ ERROR 409 - Duplicate post title:');
      console.log(`curl -X POST http://localhost:${PORT}/api/posts \\`);
      console.log(`  -H "Content-Type: application/json" \\`);
      console.log(`  -d '{"title":"My First Post","content":"Different content","authorId":1}'`);
      
      console.log('\n8️⃣ ERROR 404 - Update non-existent user:');
      console.log(`curl -X PUT http://localhost:${PORT}/api/users/999 \\`);
      console.log(`  -H "Content-Type: application/json" \\`);
      console.log(`  -d '{"firstName":"Updated"}'`);
      
      console.log('\n💡 Expected HTTP Status Codes:');
      console.log('   200 ✅ Success');
      console.log('   201 ✅ Created');
      console.log('   404 ❌ Not Found');
      console.log('   409 ❌ Conflict (unique constraint violation)');
      console.log('   422 ❌ Unprocessable Entity (validation/FK errors)');
      console.log('   500 ❌ Internal Server Error');
      
      console.log('\n🔍 Test the scenarios above to see proper error handling!');
    });

  } catch (error) {
    console.error('❌ Server startup failed:', error.message);
    process.exit(1);
  }
}

// Start the demo server
if (require.main === module) {
  startServer();
}

module.exports = { startServer };