@MatrixParam

Instead of injecting and processing PathSegment objects to obtain matrix parameter values, the JAX-RS specification allows you to inject matrix parameter values directly through the @javax.ws.rs.MatrixParam annotation. Let’s change our CarResource example from the previous section to reflect using this annotation:

@Path("/{make}")
public class CarResource {

   @GET
   @Path("/{model}/{year}")
   @Produces("image/jpeg")
   public Jpeg getPicture(@PathParam("make") String make,
                          @PathParam("model") String model,
                          @MatrixParam("color") String color) {
      ...
   }

Using the @MatrixParam annotation shrinks our code and provides a bit more readability. The only downside of @MatrixParam is that sometimes you might have a repeating matrix parameter that is applied to many different path segments in the URI. For example, what if color shows up multiple times in our car service example?

GET /mercedes/e55;color=black/2006/interior;color=tan

Here, the color attribute shows up twice: once with the model and once with the interior. Using @MatrixParam("color") in this case would be ambiguous and we would have to go back to processing PathSegments to obtain this matrix parameter.