Link relations in responses in Rest API - Step-by-Step Execution

Concept Flow - Link relations in responses

Client sends request

↓

Server processes request

↓

Server builds response

↓

Add links with relations

↓

Send response with links

↓

Client reads links

↓

Client uses links to navigate API

The client asks the server for data. The server adds links with relation names to the response. The client uses these links to find related resources.

Execution Sample

Rest API

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

{
  "data": {"id": 1, "name": "Book"},
  "links": {
    "self": "/books/1",
    "author": "/authors/42"
  }
}

This response shows a resource with links named 'self' and 'author' to help the client find related data.

Execution Table

Step	Action	Data Added	Link Relation	Link URL
1	Start building response	{}	None	None
2	Add resource data	{"id":1,"name":"Book"}	None	None
3	Add 'self' link	Same data	self	/books/1
4	Add 'author' link	Same data	author	/authors/42
5	Send response to client	Full JSON with links	All added	All URLs included
6	Client receives response	Reads data and links	Uses 'self' and 'author'	Navigates API

💡 Response sent with links; client can now use these to find related resources.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
response_body	{}	{"data":{"id":1,"name":"Book"}}	{"data":{"id":1,"name":"Book"},"links":{"self":"/books/1"}}	{"data":{"id":1,"name":"Book"},"links":{"self":"/books/1","author":"/authors/42"}}	{"data":{"id":1,"name":"Book"},"links":{"self":"/books/1","author":"/authors/42"}}

Key Moments - 3 Insights

Why do we add 'self' as a link relation in the response?

The 'self' link tells the client the exact URL of the current resource, so it can easily find or refresh it later. See step 3 in the execution_table.

Can the client use the 'author' link to get more information?

Yes, the 'author' link points to a related resource. The client can follow it to get author details. See step 4 and 6 in the execution_table.

What happens if the response has no links?

The client won't know how to find related resources easily. Links guide navigation and improve API usability. This is why links are added before sending the response (step 5).

Visual Quiz - 3 Questions

Look at the execution_table, what link relation is added at step 4?

A "self"

B "next"

C "author"

D "prev"

💡 Hint

Check the 'Link Relation' column at step 4 in the execution_table.

At which step does the client receive the full response with links?

A Step 5

B Step 3

C Step 2

D Step 1

💡 Hint

Look for when the response is sent to the client in the execution_table.

If we remove the 'self' link at step 3, what changes in variable_tracker?

A response_body will have only 'author' link

B response_body will not have 'self' in links

C response_body will be empty

D response_body will have no links at all

💡 Hint

Check the 'response_body' values after step 3 in variable_tracker.

Concept Snapshot

Link relations in responses:
- Add 'links' object in JSON response
- Each link has a relation name (e.g., 'self', 'author')
- 'self' points to current resource URL
- Other links point to related resources
- Helps client navigate API easily

Full Transcript

When a client asks a server for data, the server sends back the data plus helpful links. These links have names called relations, like 'self' for the current item or 'author' for related info. The client reads these links to find more data without guessing URLs. This makes using the API easier and clearer.

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