HTTP Content Negotiation - RESTful Java with JAX-RS 2.0 - page 135

Here, we create a Response with the ResponseBuilder interface, using the desired media
type and language pulled directly from the HttpHeaders injected object.

Variant processing

JAX-RS also has an API to dealwith situations in which you have multiple sets of media
types, languages, and encodings you have to match against. You can use the interface
javax.ws.rs.core.Request and the class javax.ws.rs.core.Variant to perform these
complex mappings. Let's look at the Variant class first:

package package javax . ws . rs . core . Variant

public public class class Variant Variant {

public public Variant ( MediaType mediaType , Locale language , String encoding ) {...}

public public Locale getLanguage () {...}

public public MediaType getMediaType () {...}

public public String getEncoding () {...}

}

The Variant class is a simple structure that contains one media type, one language, and one
encoding. It represents a single set that your JAX-RS resource method supports. You build a
list of these objects to interact with the Request interface:

package package javax . ws . rs . core . Request

public public interface interface Request Request {

Variant selectVariant ( List < Variant > variants ) throws throws IllegalArgumentException ;

...
}

The selectVariant() method takes in a list of Variant objects that your JAX-RS method
supports. It examines the Accept , Accept-Language , and Accept-Encoding headers of the
incoming HTTP request and compares them to the Variant list you provide to it. It picks the
variant that best matches the request. More explicit instances are chosen before less explicit
ones. The method will return null if none of the listed variants matches the incoming accept
headers. Here's an example of using this API:

@Path ( "/myservice" )
public

public class class MyService MyService {