CRUD Operations with HTTP

CRUD (Create, Read, Update, Delete) operations are the four basic functions of persistent storage. REST maps these operations to HTTP methods in a standardized way.

CRUD to HTTP Mapping

CRUD	HTTP Method	URI Pattern	Description
Create	POST	/resources	Create a new resource
Read	GET	/resources	List all resources
Read	GET	/resources/\{id\}	Get a specific resource
Update	PUT	/resources/\{id\}	Replace a resource
Update	PATCH	/resources/\{id\}	Partially update a resource
Delete	DELETE	/resources/\{id\}	Remove a resource

Complete CRUD Example: User Management

Let's walk through a complete CRUD implementation for a user resource.

Create (POST)

POST /api/users HTTP/1.1
Content-Type: application/json

{
  "name": "Alice Smith",
  "email": "alice@example.com",
  "department": "Engineering"
}

Success Response:

HTTP/1.1 201 Created
Location: /api/users/42
Content-Type: application/json

{
  "id": 42,
  "name": "Alice Smith",
  "email": "alice@example.com",
  "department": "Engineering",
  "createdAt": "2024-01-15T10:30:00Z"
}

Read Collection (GET)

GET /api/users HTTP/1.1
Accept: application/json

Response:

HTTP/1.1 200 OK
Content-Type: application/json

{
  "data": [
    { "id": 1, "name": "Alice Smith", "email": "alice@example.com" },
    { "id": 2, "name": "Bob Jones", "email": "bob@example.com" }
  ],
  "total": 2
}

Read Single Resource (GET)

GET /api/users/42 HTTP/1.1
Accept: application/json

Response:

HTTP/1.1 200 OK
Content-Type: application/json

{
  "id": 42,
  "name": "Alice Smith",
  "email": "alice@example.com",
  "department": "Engineering",
  "createdAt": "2024-01-15T10:30:00Z"
}

Update - Full Replace (PUT)

PUT /api/users/42 HTTP/1.1
Content-Type: application/json

{
  "name": "Alice Johnson",
  "email": "alice.johnson@example.com",
  "department": "Product"
}

Response:

HTTP/1.1 200 OK
Content-Type: application/json

{
  "id": 42,
  "name": "Alice Johnson",
  "email": "alice.johnson@example.com",
  "department": "Product",
  "updatedAt": "2024-01-16T14:20:00Z"
}

Update - Partial (PATCH)

PATCH /api/users/42 HTTP/1.1
Content-Type: application/json

{
  "department": "Design"
}

Response:

HTTP/1.1 200 OK
Content-Type: application/json

{
  "id": 42,
  "name": "Alice Johnson",
  "email": "alice.johnson@example.com",
  "department": "Design",
  "updatedAt": "2024-01-17T09:15:00Z"
}

Delete (DELETE)

DELETE /api/users/42 HTTP/1.1

Response:

HTTP/1.1 204 No Content

Exercise: Build CRUD Requests

PUT vs PATCH: When to Use Which

This is a common source of confusion. Here's how to decide:

Use PUT when:

• You're replacing the entire resource
• The client has the complete, updated representation
• Missing fields should be set to null or defaults

PUT /users/1
{ "name": "Alice", "email": "alice@example.com", "role": "admin" }
// All fields must be provided

Use PATCH when:

• You're updating only specific fields
• You want to leave other fields unchanged
• You're making a small change to a large resource

PATCH /users/1
{ "role": "admin" }
// Only role changes, name and email stay the same

Nested Resource CRUD

For nested resources, CRUD works within the parent context:

POST   /users/1/orders          # Create order for user 1
GET    /users/1/orders          # List user 1's orders
GET    /users/1/orders/99       # Get specific order
PUT    /users/1/orders/99       # Replace order
PATCH  /users/1/orders/99       # Update order
DELETE /users/1/orders/99       # Delete order

Summary

Operation	Method	Collection URI	Resource URI
Create	POST	/items	-
List	GET	/items	-
Read	GET	-	/items/\{id\}
Replace	PUT	-	/items/\{id\}
Update	PATCH	-	/items/\{id\}
Delete	DELETE	-	/items/\{id\}

Understanding the CRUD-to-HTTP mapping is essential for designing consistent REST APIs.