Link relations in responses in Rest API - Mini Project: Build & Apply

Link relations in REST API responses

📖 Scenario: You are building a simple REST API that returns information about books. To help clients navigate your API easily, you want to include link relations in the JSON responses. These links tell clients where to find related resources, like the author's details or the list of all books.

🎯 Goal: Create a JSON response for a book that includes _links with link relations for self, author, and all_books. This helps API users understand how to get more information.

📋 What You'll Learn

Create a dictionary called book with keys id, title, and author_id with exact values

Create a variable called base_url with the string "https://api.example.com/books"

Add a key _links to the book dictionary with nested dictionaries for self, author, and all_books containing exact URLs

Print the book dictionary as a JSON string with indentation

💡 Why This Matters

🌍 Real World

APIs often include link relations in responses to guide clients to related data easily, improving usability and discoverability.

💼 Career

Understanding how to add link relations is important for backend developers working with REST APIs to create clear, navigable responses.

1

Create the initial book data

Create a dictionary called book with these exact entries: 'id': 101, 'title': 'Learn REST APIs', and 'author_id': 5.

Rest API

# Create the book dictionary with id, title, and author_id
# Your code here

Hint

Use curly braces {} to create a dictionary with the exact keys and values.

2

Add the base URL variable

Create a variable called base_url and set it to the string "https://api.example.com/books".

Rest API

book = {'id': 101, 'title': 'Learn REST APIs', 'author_id': 5}
# Create the base_url variable with the API base URL
# Your code here

Hint

Use quotes to create a string and assign it to base_url.

3

Add link relations to the book dictionary

Add a key _links to the book dictionary. It should be a dictionary with keys self, author, and all_books. Each key should map to a dictionary with a key href and the exact URLs: self is f"{base_url}/{book['id']}", author is f"https://api.example.com/authors/{book['author_id']}", and all_books is base_url.

Rest API

book = {'id': 101, 'title': 'Learn REST APIs', 'author_id': 5}
base_url = "https://api.example.com/books"
# Add the _links dictionary with self, author, and all_books URLs
# Your code here

Hint

Use f-strings to build URLs using base_url and values from book.

4

Print the JSON response

Import the json module and print the book dictionary as a JSON string with indentation of 2 spaces using json.dumps().

Rest API

book = {'id': 101, 'title': 'Learn REST APIs', 'author_id': 5}
base_url = "https://api.example.com/books"
book['_links'] = {
    'self': {'href': f"{base_url}/{book['id']}"},
    'author': {'href': f"https://api.example.com/authors/{book['author_id']}"},
    'all_books': {'href': base_url}
}
# Import json and print the book dictionary as JSON with indent=2
# Your code here

Hint

Use import json at the top, then print(json.dumps(book, indent=2)) to show the JSON nicely.

Practice

1. What is the main purpose of using link relations in REST API responses?

easy

A. To define the HTTP methods allowed on a resource

B. To encrypt the data sent between client and server

C. To specify the data format like JSON or XML

D. To describe how different resources are connected and provide URLs for related actions

Solution

1. Step 1: Understand link relations concept

   Link relations describe the relationship between resources and provide URLs to related resources or actions.

2. Step 2: Identify the purpose in REST API responses

   They help clients navigate the API by following links instead of hardcoding URLs.

3. Final Answer:

   To describe how different resources are connected and provide URLs for related actions -> Option D

4. Quick Check:

   Link relations = resource connections and URLs [OK]

Hint: Link relations connect resources with URLs in responses [OK]

Common Mistakes:

• Confusing link relations with data encryption
• Thinking link relations define data format
• Mixing link relations with HTTP method definitions

2. Which of the following is the correct way to include a link relation in a JSON REST API response?

easy

A. "_links": { "self": { "href": "/users/123" } }

B. "links": [ { "url": "/users/123" } ]

C. "link": "/users/123"

D. "href": { "self": "/users/123" }

Solution

1. Step 1: Recall standard link relation format in JSON

   Standard uses a _links object with named relations like self containing an href URL.

2. Step 2: Match the correct JSON structure

   "_links": { "self": { "href": "/users/123" } } matches this format exactly, others do not follow the standard naming or structure.

3. Final Answer:

   "_links": { "self": { "href": "/users/123" } } -> Option A

4. Quick Check:

   Standard link relation = _links with self and href [OK]

Hint: Look for _links with self and href keys [OK]

Common Mistakes:

• Using 'links' instead of '_links'
• Missing 'href' inside the relation object
• Using arrays instead of objects for link relations

3. Given this JSON response snippet:

{
  "_links": {
    "self": { "href": "/orders/42" },
    "cancel": { "href": "/orders/42/cancel" }
  }
}

What URL should a client use to cancel order 42?

medium

A. /orders/42

B. /orders/cancel/42

C. /orders/42/cancel

D. /orders/42/cancelled

Solution

1. Step 1: Locate the 'cancel' link relation in the JSON

   The 'cancel' relation has the href value "/orders/42/cancel" which is the URL to cancel the order.

2. Step 2: Confirm the correct URL for cancellation

   The client should use the URL exactly as given in the 'cancel' href to perform the cancel action.

3. Final Answer:

   /orders/42/cancel -> Option C

4. Quick Check:

   Cancel URL = /orders/42/cancel [OK]

Hint: Use the href under the 'cancel' link relation [OK]

Common Mistakes:

• Using the 'self' URL instead of 'cancel'
• Rearranging URL parts incorrectly
• Guessing URL instead of reading from response

4. You receive this partial JSON response:

{
  "_links": {
    "self": { "href": "/products/7" },
    "edit": { "url": "/products/7/edit" }
  }
}

What is wrong with the link relations in this response?

medium

A. The 'edit' relation uses 'url' instead of 'href'

B. The 'self' relation should not be included

C. The 'href' value for 'self' is missing a domain

D. The '_links' key should be named 'links'

Solution

1. Step 1: Check the property names inside link relations

   Standard link relations use 'href' to specify the URL, not 'url'.

2. Step 2: Identify the incorrect property

   The 'edit' relation incorrectly uses 'url' instead of 'href'.

3. Final Answer:

   The 'edit' relation uses 'url' instead of 'href' -> Option A

4. Quick Check:

   Link relation URLs must use 'href' key [OK]

Hint: Link URLs always use 'href', not 'url' [OK]

Common Mistakes:

• Thinking 'url' is acceptable instead of 'href'
• Expecting full domain in href for relative URLs
• Renaming '_links' to 'links' incorrectly

5. You want to design a REST API response for a blog post that includes links to the post itself, the author's profile, and comments. Which JSON structure correctly uses link relations to represent these?

hard

A. { "links": [ { "rel": "self", "url": "/posts/10" }, { "rel": "author", "url": "/users/5" }, { "rel": "comments", "url": "/posts/10/comments" } ] }

B. { "_links": { "self": { "href": "/posts/10" }, "author": { "href": "/users/5" }, "comments": { "href": "/posts/10/comments" } } }

C. { "_links": { "self": "/posts/10", "author": "/users/5", "comments": "/posts/10/comments" } }

D. { "_links": { "self": { "url": "/posts/10" }, "author": { "url": "/users/5" }, "comments": { "url": "/posts/10/comments" } } }

Solution

1. Step 1: Recall the correct link relation format

   Each link relation should be an object with an 'href' key inside the '_links' object.

2. Step 2: Evaluate each option's structure

   { "_links": { "self": { "href": "/posts/10" }, "author": { "href": "/users/5" }, "comments": { "href": "/posts/10/comments" } } } correctly uses '_links' with 'self', 'author', and 'comments' keys, each having an 'href' URL. Options B and D use 'url' instead of 'href', and C uses strings instead of objects.

3. Final Answer:

   { "_links": { "self": { "href": "/posts/10" }, "author": { "href": "/users/5" }, "comments": { "href": "/posts/10/comments" } } } -> Option B

4. Quick Check:

   Use '_links' with objects containing 'href' URLs [OK]

Hint: Use '_links' with 'href' keys for each relation [OK]

Common Mistakes:

• Using 'url' instead of 'href' for links
• Using arrays instead of objects for link relations
• Assigning string URLs directly without 'href' objects