Link relations in responses in Rest API - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a link relation in REST API responses?

A link relation is a named relationship between the current resource and another resource, usually provided as a URL in the response to guide clients on what actions or resources are related.

beginner

Why are link relations useful in REST API responses?

They help clients discover related resources dynamically without hardcoding URLs, making APIs more flexible and easier to navigate.

beginner

Give an example of a common link relation name.

Common link relation names include self (link to the current resource), next (link to the next page), and prev (link to the previous page).

intermediate

How are link relations typically represented in JSON API responses?

They are often included in a _links or links object, where each key is a relation name and the value is a URL string or an object with href and other metadata.

intermediate

What is the benefit of using standard link relation names?

Standard names improve interoperability because clients and developers recognize common relations and understand their meaning without extra documentation.

What does the self link relation usually represent in a REST API response?

A The URL of a related but unrelated resource

B The URL of the current resource

C The URL of the previous resource

D The URL of the next resource

The self relation points to the current resource's URL.

Where are link relations commonly included in a JSON API response?

A In the <code>_links</code> or <code>links</code> object

B In the HTTP headers only

C Inside the main data object without keys

D In the URL query parameters

Link relations are usually included in a dedicated _links or links object in the JSON response body.

Why should APIs use standard link relation names?

A To confuse clients

B To make URLs longer

C To improve interoperability and understanding

D To hide resource URLs

Standard names help clients understand the meaning of links without extra documentation.

Which of the following is NOT a typical link relation name?

A next

B prev

C self

D random

random is not a standard or common link relation name.

How do link relations help REST API clients?

A By dynamically discovering related resources

B By hardcoding URLs

C By encrypting data

D By reducing server load

Link relations guide clients to related resources dynamically, avoiding hardcoded URLs.

Explain what link relations are and why they are important in REST API responses.

Think about how clients find related resources without guessing URLs.

Describe how link relations are typically structured in a JSON API response and give examples of common relation names.

Consider the JSON format that groups related URLs.

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