HATEOAS - Hypermedia as the Engine of Application State

Just came across this term HATEOAS , which some of my team members were using in describing what we did in our previous project wrt to REST.


My Last project was about building an e-commerce platform for one of the largest book publisher and distributor in Latin America.As part of that project we had thought to use the LEVEL-3 for rest communication which is using REST as a hypermedia controls. 


You can read about different levels of REST at this Martin Fowler’s Blog .


When we said we wanted to use REST as hypermedia controls , the main idea behind this was to be able to navigate the result of a REST call.


For Example if there is a product catalogue call which looks like



GET /products/123456



So It would return 


As you can see that apart from the the properties of the product 123456 it also has a links array.


This links array contains the the link description in rel and the location of that document.


so essentially what i could do is parse the JSON response , and then look for what all things can be done on that product.In this case we have exposed two actions , one for the self and the other to place an order for that product.Then to place an order would be to simple do a post on the the href for rel = “order”


The biggest advantage of this scheme is that , you are not dependent on the uri schemes of API , since every time you are navigating the href , if if the API provider changes the url’s you will not be affected . All you need is an entry point in the API and then you can navigate from there on.


This specifically helps during the development process too , as you can change the routes of the API without worrying about breaking the tests anywhere else .

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