There is an emergence of non-HTML HTTP applications ("Web APIs") which use hyperlinks to direct clients around their resources. HAL presents two hypermedia types, one for XML and one for JSON. Typically, the type is only relevant for resources returned by the API, as relational links are not usually submitted when creating, updating, or deleting resources. Implementing a HAL hypermedia REST API using Spring HATEOAS and Spring Boot. This is necessary because JSON has no specific semantics around linking, and XML, while it has some semantics, does not cover how to provide multiple links for a given element.
HAL addresses JSON by reserving a special _links property, and. It provides a small set of conventions on top of JSON and XML for expressing hyperlinks to, and embeddedness of, related resources. Traverson plug-in that adds support for the JSON dialect of HAL, the hypertext application language to Traverson. The spec is here: hal_specification. Internally, traverson- hal uses Halfred to work with HAL resources. While in theory you could use Traverson even without special support for HAL by specifying each link relation.
Hypertext Application Language ( HAL ) is an Internet Draft (a "work in progress") standard convention for defining hypermedia such as links to external resources within JSON or XML code. In particular, it describes how to design JSON representations, although there is a XML counterpart too. HAL is a simple way of linking with JSON or XML. HAL is (I hope by purpose) not differentiating between various rels.
It defines that if the templated attribute is set to true, the href attribute is a URI template. Short Answer: CURIEs provide a shortcut or template for linking to API documentation within a HAL based API response. If you link is templated, you can set parameter to fetch to compute fetch URL. Resources can contain State defined by key-value pairs of data, Links leading to additional resources and Embedded Resources which are children of the current resource embedded in the. A HAL API should be navigated from its root. The root itself is a collection of links. This indicates the semantic, the meaning, of a particular link.
Here we see the link self, which is the uri for this user, and the team it belongs to.
The purpose of HAL is make APIs "discoverable" – it defines a set of conventions that allow consumers of your API to follow links between resources, as well as providing pagination and other convenience features for "exploring" an API. So first off is HAL, which is actually the hypermedia implementation supported out of the box by Spring in the Spring HATEOAS library. As representations for REST web services are usually rendered in either XML or JSON the natural choice of technology to achieve this is either Jackson, JAXB, or both in combination.
To follow HATEOAS principles you need to incorporate links into those representation. The way a relationship should be expressed in HAL is using a link. This post shows some of the widely used JSON media types and how they deal with links. Disclaimer: In the previous years I implemented HAL or several.
Example files for all of them are in this json links gist. HAL stands for Hypermedia Application Language and it is simple, elegant and powerful. Learn the many ways to add linking and resource expansion to your REST JSON API, and the particularly elegant approach taken by Stormpath. For contrast, you can see how this differs from a HAL example below, which shows all of the links defined in a separate array of objects.
If you want to embed links in your JSON, you should put them under an _links key and.