POST for creating resources in Rest API - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the HTTP status code returned after a successful POST request?

Consider a REST API where you send a POST request to create a new user. The server successfully creates the user and returns a response.

What is the typical HTTP status code you expect in the response?

A 200 OK

B 404 Not Found

C 500 Internal Server Error

D 201 Created

💡 Hint

Think about the status code that indicates a new resource was successfully created.

201 Created is the standard status code returned when a POST request successfully creates a new resource.

❓ Predict Output

intermediate

What is the response body after creating a resource with POST?

You send a POST request to create a new book resource. The server responds with JSON containing the new book's ID and title.

What is the expected JSON response body?

Rest API

POST /books HTTP/1.1
Host: example.com
Content-Type: application/json

{"title": "Learn REST"}

A {"id": 101, "title": "Learn REST"}

B {"error": "Missing title"}

C {"status": "success"}

D {}

💡 Hint

The server usually returns the created resource with its new ID.

After creating a resource, the server often returns the full resource including its new unique ID.

🔧 Debug

advanced

Why does this POST request return 400 Bad Request?

Examine the following POST request code snippet. It tries to create a new user but the server returns a 400 Bad Request error.

POST /users HTTP/1.1
Host: api.example.com
Content-Type: application/json

{"username": "", "email": "[e-mail]"}

What is the most likely cause of the 400 error?

A The email field is missing

B The Content-Type header is missing

C The username field is empty, violating validation rules

D The HTTP method should be GET instead of POST

💡 Hint

Check the data sent in the request body for required fields.

A 400 Bad Request often means the server rejected the input data. An empty username likely violates validation rules.

🧠 Conceptual

advanced

Which header is important to include in a POST request with JSON data?

When sending a POST request with JSON data to create a resource, which HTTP header must you include to inform the server about the data format?

A Content-Type

B Authorization

C Accept-Encoding

D Cache-Control

💡 Hint

This header tells the server what format the request body is in.

The Content-Type header specifies the media type of the request body, such as application/json.

❓ Predict Output

expert

What is the value of the Location header after a successful POST?

A POST request creates a new resource at the server. The server responds with status 201 Created and includes a Location header.

What does the Location header contain?

A The URL of the POST endpoint

B The URL of the newly created resource

C The client's IP address

D The server's root URL

💡 Hint

The Location header tells the client where to find the new resource.

The Location header contains the URL of the newly created resource so the client can access it directly.

Practice

1. What is the primary purpose of the POST method in REST APIs?

easy

A. To create a new resource on the server

B. To retrieve data from the server

C. To update an existing resource completely

D. To delete a resource from the server

Solution

1. Step 1: Understand HTTP methods

   HTTP methods have specific roles: GET retrieves, POST creates, PUT updates, DELETE removes.

2. Step 2: Identify POST's role

   POST sends data to the server to create a new resource, unlike GET which only fetches data.

3. Final Answer:

   To create a new resource on the server -> Option A

4. Quick Check:

   POST = Create resource [OK]

Hint: POST is for sending data to create something new [OK]

Common Mistakes:

• Confusing POST with GET which only fetches data
• Thinking POST updates existing resources fully
• Assuming POST deletes resources

2. Which of the following is the correct way to send data in a POST request to create a resource?

easy

A. Include data in the URL query parameters

B. Send data in the request body as JSON

C. Send data as HTTP headers

D. Send data as a cookie

Solution

1. Step 1: Identify where POST data goes

   POST requests send data in the request body, not in URL or headers.

2. Step 2: Recognize common data format

   JSON is the standard format for sending structured data in the body for REST APIs.

3. Final Answer:

   Send data in the request body as JSON -> Option B

4. Quick Check:

   POST data = request body JSON [OK]

Hint: POST data goes in the body, not URL or headers [OK]

Common Mistakes:

• Putting data in URL query instead of body
• Trying to send data via headers
• Using cookies to send creation data

3. Given this Python code using the requests library, what will be the HTTP status code if the resource is created successfully?

import requests
url = 'https://api.example.com/items'
data = {'name': 'Book', 'price': 12.99}
response = requests.post(url, json=data)
print(response.status_code)

medium

A. 200

B. 404

C. 201

D. 500

Solution

1. Step 1: Understand POST success codes

   When a resource is created, the server usually returns HTTP status 201 Created.

2. Step 2: Analyze the code behavior

   The code sends a POST request with JSON data; if successful, response.status_code will be 201.

3. Final Answer:

   201 -> Option C

4. Quick Check:

   POST success = 201 Created [OK]

Hint: 201 means resource created successfully [OK]

Common Mistakes:

• Confusing 200 OK with 201 Created
• Assuming 404 means success
• Thinking 500 means success

4. You wrote this POST request code but get a 400 Bad Request error. What is the likely problem?

import requests
url = 'https://api.example.com/users'
data = {'username': 'alice'}
response = requests.post(url, data=data)
print(response.status_code)

medium

A. The data should be sent as JSON, not form data

B. The URL is incorrect for POST requests

C. POST requests cannot send data

D. The server does not support HTTPS

Solution

1. Step 1: Check data sending method

   Using data=data sends form-encoded data, but API expects JSON for POST creation.

2. Step 2: Fix data format

   Use json=data in requests.post to send JSON body, which the server accepts.

3. Final Answer:

   The data should be sent as JSON, not form data -> Option A

4. Quick Check:

   Send JSON with json= parameter [OK]

Hint: Use json= not data= to send JSON body [OK]

Common Mistakes:

• Sending form data instead of JSON
• Assuming URL is wrong without checking
• Thinking POST can't send data
• Ignoring HTTPS requirement

5. You want to create a new blog post resource with title and content using a POST request. Which of these JSON payloads correctly represents the data to send in the request body?

hard

A. ["title", "My Day", "content", "It was sunny."]

B. "title=My Day&content=It was sunny."

C. {"My Day": "title", "It was sunny.": "content"}

D. {"title": "My Day", "content": "It was sunny."}

Solution

1. Step 1: Understand JSON object structure

   JSON objects use key-value pairs with keys as strings and values as data.

2. Step 2: Identify correct JSON format

   {"title": "My Day", "content": "It was sunny."} correctly uses keys "title" and "content" with their string values in an object.

3. Final Answer:

   {"title": "My Day", "content": "It was sunny."} -> Option D

4. Quick Check:

   JSON object with keys and values = {"title": "My Day", "content": "It was sunny."} [OK]

Hint: JSON data must be key-value pairs inside braces {} [OK]

Common Mistakes:

• Using JSON arrays instead of objects
• Swapping keys and values
• Sending URL-encoded string instead of JSON