Request & Response

About

At the heart of every API interaction is a request-response cycle. Whether you’re calling an external service or communicating between internal systems, this exchange is how APIs operate. One side sends a request, and the other returns a response.

What is a Request?

A request is what an API consumer (client) sends to an API provider (server) to ask for something. It could be asking for data, creating a new record, updating existing information, or deleting something.

Every API request has several key components:

1. URL (Uniform Resource Locator)

• The address of the resource you're trying to access.

• Example: https://api.example.com/products/42

2. HTTP Method (Verb)

• Tells the server what action to perform:

  • GET: Retrieve data

  • POST: Create new data

  • PUT/PATCH: Update existing data

  • DELETE: Remove data

3. Headers

• Contain metadata about the request.

• Examples:

  • Content-Type: application/json

  • Authorization: Bearer <token>

4. Query Parameters / Path Parameters

• Used to filter or identify specific resources.

• Query: /users?role=admin

• Path: /users/123

5. Request Body (Optional)

• Used with methods like POST or PUT.

• Contains data to be sent to the server, usually in JSON format.

{
  "name": "Alice",
  "email": "[email protected]"
}

What Is a Response?

The response is the reply from the server after processing the request. It lets the client know whether the request was successful, and includes any data or error message.

A response consists of:

1. Status Code

• Indicates the result of the request.

  • 200 OK – Successful

  • 201 Created – Resource created

  • 400 Bad Request – Problem with the request

  • 401 Unauthorized – Invalid credentials

  • 500 Internal Server Error – Something failed on the server

2. Headers

• Provide metadata, such as:

  • Content-Type: application/json

  • Cache-Control: no-cache

3. Response Body (Usually JSON)

• Contains the actual data or an error message.

• Example:

jsonCopyEdit{
  "id": 42,
  "name": "Laptop",
  "price": 599.99
}

Example

Request

GET /products/42
Host: api.shop.com
Authorization: Bearer eyJhbGciOiJIUzI1Ni...
Accept: application/json

Response

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

{
  "id": 42,
  "name": "Wireless Mouse",
  "price": 29.99
}