While viewing a web page, you can see data in the page and perform actions with it. How about a REST API? Typically when you ask for a REST Resource, you get the details of the resource back. How about sending the operations that you can do with the resource in the response?

We learn

  • What is HATEOAS?
  • Why do you need to use HATEOAS?
  • When do you make use of HATEOAS?


This is the fifth article in a series of articles on REST APIs:

What Does HATEOAS Stand For?

The term HATEOAS stands for the phrase Hypermedia As The Engine Of Application State. To understand this further, we first need to understand the meaning of Hypermedia.

What Does Hypermedia Mean?

Have a look at the following web page:

image info

When the browser load the page, you definitely can see all the content that page has to offer. More interestingly, the page also allows you to perform a lot of actions around that data, such as:

  • Clicking on buttons (the green “Clone or Download”)
  • Clicking on tabs (to view the “Issues”, for instance),

and several more.

Now let’s look at how our REST API’s behave:

If you look at a typical GET request to a RESTful server, such as this one:

image info

The request to GET http://localhost:8080/users retrieves a set of three users details in this case. Sending a request with GET http://localhost:8080/users/1 will retrieve details of just the first user.

Typically, when we perform a REST request, we only get the data, and not any actions around it. This is where HATEOAS comes in the fill in the gap.

A HATEOAS request allows you to not only send the data but also specify the related actions:

image info

This example was in the JSON format. An XML format for another example would look something like this:

image info

When you send out this request to retrieve account details, you get both:

  • Account number and balance details
  • Links that provide actions to do a deposit/withdrawal/transfer/closure

With HATEOAS, a request for a REST resource gives me both data, and actions related to the data.

Why Do We Need HATEOAS?

The single most important reason for HATEOAS is loose coupling. If a consumer of a REST service needs to hard-code all the resource URLS, then it is tightly coupled with your service implementation. Instead, if you return the URLs it could use for the actions, then it is loosely coupled. There is no tight dependency on the URI structure, as it is specified and used from the response.

A few significant topics related to HATEOAS are:

HAL - Hypertext Application Language

When you design a RESTful service, there is need to specify how to return data and links corresponding to a request. HAL is a simple format that gives a easy, consistent way to hyperlink between resources in your REST API. Here is an example:

image info

With HAL, you have a few categories of representations:

  • Links: Specified as combination of
    • Target - Given as a URI
    • Relation - A name
  • Embedded Resources: Other resources contained within a given REST resource
  • State: The actual resource data

If you happen to use the Spring Framework to develop your REST service, then Spring HATEOAS is a good engine to use for your service.

Do check out our video on this:

image info


In this article, we looked at what HATEOAS stands for. With HATEOAS, responses to REST requests return not just the data, but also actions that can be performed with the resource. This helps in making the applications loosely coupled.

10 Step Reference Courses

Image Image Image Image Image

in28Minutes is helping 300,000 Learners across the world reach their learning goals. Click here for the complete catalogue of 30 Courses.

Related Posts

Spring Boot Tutorials for Beginners

At in28Minutes, we are creating a number of tutorials with videos, articles & courses on Spring Boot for Beginners and Experienced Developers. This resources will help you learn and gain expertise at Spring Boot.

Spring and Spring Boot Video Tutorials for Beginners

At in28Minutes, we are creating a number of tutorials with videos, articles & courses on Spring Boot for Beginners and Experienced Developers. Here's a list of video tutorials and courses for you

Software Design - Separation Of Concerns - with examples

Software architects and programmers love having Seperation of Concerns. What is it? Why is it important? Let's get started.

Object Oriented Software Design - Solid Principles - with examples

Software design is typically complex. Object oriented design takes it to the next level. There are a number of design patterns and other stuff to be aware of. Can we make things simple? What are the goals to aim for when you are doing object oriented design? SOLID Principles is a great starting point for Object Oriented Design.

Software Design - Open Closed Principle - with examples

Open Closed Principle is one of the SOLID Principles. You want your code to be easily extended. How do you achieve it with minimum fuss? Let's get started.

Software Design - What is Dependency Inversion Principle?

Dependency Inversion Principle is one of the important SOLID Principles. Dependency Inversion Principle is implemented by one of the most popular Java frameworks - Spring. What is it all about? How does it help you design good applications?

Introduction to Four Principles Of Simple Design

With agile and extreme programming, the focus is on keeping your design simple. How do you keep your design simple? How do you decide whether your code is good enough?

Software Design - Single Responsibility Principle - with examples

For me, Single Responsibility Principle is the most important design principle. What is Single Responsibility Principle? How do you use it? How does it help with making your software better? Let's get started.

REST API Best Practices - With Design Examples from Java and Spring Web Services

Designing Great REST API is important to have great microservices. How do you design your REST API? What are the best practices?

Designing REST API - What is Code First Approach?

Designing Great REST API is important to have great microservices. Code First approach focuses on generating the contract from code. Is it the best possible approach?