gistfile1.java

@Path("/user")
public class UserResource {

	@PUT
	@Path("{username: [a-zA-Z][a-zA-Z_0-9]*}")
	@Consumes("application/json, application/xml")
	@Produces("application/json, application/xml")
	public Response updateUser(@PathParam("username") String userName) {
		//Do your thing here… ;)
	}
}