API Development and Integration

Chapter 5: Request and Response Formats

5.1 JSON Format

JSON (JavaScript Object Notation) is the standard format for REST API communication.

// Request body (POST/PUT/PATCH)
{
    "name": "John Doe",
    "email": "john@example.com",
    "age": 30
}

// Response format
{
    "success": true,
    "data": {
        "id": 1,
        "name": "John Doe",
        "email": "john@example.com"
    }
}

// Error response
{
    "success": false,
    "error": {
        "message": "Validation failed",
        "code": "VALIDATION_ERROR",
        "details": [
            { "field": "email", "message": "Invalid email format" }
        ]
    }
}

5.2 Content Negotiation

// Accept different formats
app.get('/api/users/:id', (req, res) => {
    const accept = req.headers.accept;
    
    if (accept.includes('application/xml')) {
        res.type('xml');
        res.send(convertToXML(user));
    } else {
        res.json(user);
    }
});

5.3 Request Validation

// Validate request body
const { body, validationResult } = require('express-validator');

app.post('/api/users',
    body('email').isEmail().normalizeEmail(),
    body('name').trim().isLength({ min: 2, max: 50 }),
    body('age').isInt({ min: 0, max: 120 }),
    (req, res) => {
        const errors = validationResult(req);
        if (!errors.isEmpty()) {
            return res.status(400).json({ errors: errors.array() });
        }
        // Process valid request
    }
);