HATEOAS - RESTful Java with JAX-RS 2.0

Java Reference

In-Depth Information

HTTP

HTTP / 1.1 200 OOK

Content-Type : application/xml

Link: <http://example.com/orders/333/cancelled>; rel=cancel

...

</order>

The Link header has all the same characteristics as an Atom link. The URI is enclosed within

<> followed by one or more attributes delimited by semicolons. The rel attribute is required

and means the same thing as the corresponding Atom attribute of the same name. This part

isn't shown in the example, but you may also specify a media type via the type attribute.

Personally, I really like Link headers as an alternative to embedding Atom links. Many

times, I find that my client isn't interested in the resource representation and is only interes-

ted in the link relations. You shouldn't have to parse a whole XML or JSON document just to

find the URL you're interested in invoking on. Another nice thing is that instead of doing a

GET invocation, you can do a HEAD invocation and avoid getting the XML document en-

tirely. In general, I like to use Atom links for data aggregation and Link headers for

everything else.

HATEOAS and JAX-RS

JAX-RS doesn't have many facilities to help with HATEOAS. HATEOAS is defined by the

application, so there's not much a framework can add. What it does have, though, are helper

classes that you can use to build the URIs that you link to in your data formats.

Building URIs with UriBuilder

One such helper class is javax.ws.rs.core.UriBuilder . The UriBuilder class allows

you to construct a URI piece by piece and is also sensitive to template parameters:

public

public abstract

abstract class

class UriBuilder

UriBuilder {

public

public static

static UriBuilder fromUri ( URI uri )

throws