Why REST APIs exist

Introduction

REST APIs exist to help different computer programs talk to each other easily over the internet. They make sharing data and actions simple and organized.

When you want a mobile app to get data from a website's server.

When different software systems need to work together and share information.

When you want to let other developers use your service or data safely.

When you want to separate the user interface from the data handling on the server.

When you want to build scalable and easy-to-maintain web services.

Syntax

Rest API

REST API is not a code syntax but a style. It uses HTTP methods like GET, POST, PUT, DELETE to perform actions on resources identified by URLs.

REST stands for Representational State Transfer.

It uses standard web protocols, so it works well with browsers and servers.

Examples

Get information about the user with ID 123.

Rest API

GET /users/123

Create a new user named Alice by sending data to the server.

Rest API

POST /users
{
  "name": "Alice",
  "email": "[e-mail]"
}

Update the email of user 123.

Rest API

PUT /users/123
{
  "email": "[e-mail]"
}

Remove the user with ID 123 from the system.

Rest API

DELETE /users/123

Sample Program

This Python program uses a REST API to get user information from a public test service. It prints the user's name if successful.

Rest API

import requests

# Get user data from a REST API
response = requests.get('https://jsonplaceholder.typicode.com/users/1')

if response.status_code == 200:
    user = response.json()
    print(f"User name: {user['name']}")
else:
    print("Failed to get user data")

Important Notes

REST APIs use simple URLs and HTTP methods, making them easy to understand and use.

They help keep the client (like a web or mobile app) and server separate, so each can change independently.

Using REST APIs allows many different devices and programs to work together smoothly.

Summary

REST APIs let programs communicate over the internet using simple rules.

They use HTTP methods to work with data resources identified by URLs.

This makes building and connecting apps easier and more flexible.

Practice

1. Why do REST APIs exist in software development?

easy

A. To allow different programs to communicate over the internet using simple rules

B. To create complex user interfaces for websites

C. To store data only on local machines

D. To replace all programming languages with one standard

Solution

1. Step 1: Understand the purpose of REST APIs

   REST APIs are designed to let different software programs talk to each other over the internet easily.

2. Step 2: Compare options with this purpose

   Only To allow different programs to communicate over the internet using simple rules correctly describes this purpose. Options A, B, and C do not relate to REST APIs' main goal.

3. Final Answer:

   To allow different programs to communicate over the internet using simple rules -> Option A

4. Quick Check:

   REST APIs exist for communication = D [OK]

Hint: REST APIs help programs talk over the internet simply [OK]

Common Mistakes:

• Thinking REST APIs create user interfaces
• Believing REST APIs store data locally only
• Assuming REST APIs replace programming languages

2. Which HTTP method is commonly used in REST APIs to retrieve data from a server?

easy

A. GET

B. POST

C. DELETE

D. PUT

Solution

1. Step 1: Recall HTTP methods in REST APIs

   GET is the method used to request and retrieve data from a server.

2. Step 2: Match the method to the action

   POST sends data, DELETE removes data, PUT updates data. Only GET retrieves data.

3. Final Answer:

   GET -> Option A

4. Quick Check:

   Retrieve data = GET [OK]

Hint: GET means get data from server in REST APIs [OK]

Common Mistakes:

• Confusing POST with GET for data retrieval
• Using DELETE or PUT to get data
• Not knowing HTTP method purposes

3. What will be the output of this REST API call?

GET /users/123

Assuming user 123 exists and the API returns JSON data.

medium

A. 500 Internal Server Error

B. {"id":123,"name":"Alice"}

C. 404 Not Found

D. {"error":"User not found"}

Solution

1. Step 1: Understand the GET request to /users/123

   This request asks the server for data about user with ID 123.

2. Step 2: Check the condition given

   The user 123 exists, so the server returns the user's data in JSON format.

3. Final Answer:

   {"id":123,"name":"Alice"} -> Option B

4. Quick Check:

   Existing user GET returns data = C [OK]

Hint: GET existing user returns JSON data, not error [OK]

Common Mistakes:

• Choosing error responses when user exists
• Confusing 404 with successful data return
• Not recognizing JSON format

4. Identify the error in this REST API usage:

POST /users/123

What is wrong if the goal is to update user 123's data?

medium

A. The URL should not include the user ID

B. GET method should be used to update data

C. POST is used instead of PUT for updating existing data

D. DELETE method is required to update data

Solution

1. Step 1: Understand HTTP methods for REST APIs

   POST is usually for creating new data, PUT is for updating existing data.

2. Step 2: Match method to action

   Since the goal is to update user 123, PUT should be used instead of POST.

3. Final Answer:

   POST is used instead of PUT for updating existing data -> Option C

4. Quick Check:

   Update needs PUT, not POST = B [OK]

Hint: Use PUT to update existing data, not POST [OK]

Common Mistakes:

• Using POST to update instead of PUT
• Thinking GET updates data
• Believing DELETE updates data

5. You want to design a REST API that allows clients to list all products and add new products. Which HTTP methods and URLs should you use?

hard

A. DELETE /products to list, PUT /products to add new

B. POST /products to list, GET /products to add new

C. PUT /products to list, DELETE /products to add new

D. GET /products to list, POST /products to add new

Solution

1. Step 1: Identify methods for listing and adding

   GET is used to retrieve or list data, POST is used to create or add new data.

2. Step 2: Match methods with URLs

   Both actions use the /products URL; GET lists products, POST adds new products.

3. Final Answer:

   GET /products to list, POST /products to add new -> Option D

4. Quick Check:

   List = GET, Add = POST = A [OK]

Hint: GET lists, POST adds new resources in REST APIs [OK]

Common Mistakes:

• Swapping GET and POST roles
• Using DELETE or PUT incorrectly
• Confusing URLs for different actions