HAL format overview in Rest API - Step-by-Step Execution

Concept Flow - HAL format overview

Client sends HTTP request

↓

Server processes request

↓

Server builds HAL response

↓

Add _links

↓

Send HAL JSON response

↓

Client parses HAL response

The client sends a request, the server builds a HAL JSON response with _links and _embedded sections, then sends it back for the client to parse.

Execution Sample

Rest API

{
  "_links": {
    "self": { "href": "/orders/123" }
  },
  "total": 30
}

This is a simple HAL response showing a self link and a total value.

Execution Table

Step	Action	Data Added	Resulting JSON Part
1	Start building response	None	{}
2	Add _links section	"self": {"href": "/orders/123"}	{"_links": {"self": {"href": "/orders/123"}}}
3	Add property total	"total": 30	{"_links": {"self": {"href": "/orders/123"}}, "total": 30}
4	Send response	Complete HAL JSON	Full HAL JSON sent to client

💡 Response sent; client can now parse HAL JSON with _links and properties

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
response	{}	{"_links": {"self": {"href": "/orders/123"}}}	{"_links": {"self": {"href": "/orders/123"}}, "total": 30}	Sent to client

Key Moments - 2 Insights

Why do we use the _links section in HAL?

The _links section provides URLs to related resources, helping clients navigate the API easily, as shown in step 2 of the execution_table.

What is the purpose of the _embedded section in HAL?

The _embedded section includes related resource data directly inside the response, reducing extra requests. It is not shown in this simple example but is similar to _links in structure.

Visual Quiz - 3 Questions

Look at the execution_table at step 2, what key is added to the response?

A "_embedded"

B "_links"

C "total"

D "self"

💡 Hint

Check the 'Data Added' column at step 2 in execution_table

At which step is the 'total' property added to the response?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the 'Action' column in execution_table for when 'total' is added

If the server adds an _embedded section, where would it appear in the response building flow?

A Alongside _links before sending response

B Before adding _links

C After sending response

D After adding total property

💡 Hint

Refer to concept_flow where _links and _embedded are added before sending response

Concept Snapshot

HAL format builds JSON responses with special sections:
_links: URLs to related resources
_embedded: nested related resource data
Properties: main data fields
Client uses these to navigate and understand API easily.

Full Transcript

HAL format is a way to structure JSON responses in REST APIs. The server builds a response including a _links section with URLs to related resources and optionally an _embedded section with nested data. Properties hold main data values. The client sends a request, the server builds this HAL JSON, and sends it back. This helps clients navigate APIs easily by following links and accessing embedded data without extra requests.