# JavaEE 7 Retired The DTO

The classic DTO solves the following problem: "You want to transfer multiple data elements over a tier."


Back in the days a DTO was implemented as a Serializable anemic Java class only equipped with field accessors.


In Java EE the https://jax-rs-spec.java.net became a de-facto standard for remoting, so the implementation of Serializable interface is no more required. To transfer data between tiers in Java EE 7 you get the following options for free:


JAXB: the popular application servers offer JSON, XML serialization for "free".


@Entity
@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
@NamedQuery(name = Registration.findAll, query = "SELECT r FROM Registration r")
public class Registration {

    private static final String PREFIX = "com.airhacks.workshops.business.registrations.entity.Registration.";
    public static final String findAll = PREFIX + "all";


    @Id
    @GeneratedValue
    @XmlTransient
    private long id;

    @XmlTransient
    @Transient
    private BiFunction<Boolean, Integer, Integer> taxCalculator;

    private int numberOfDays;
    private int numberOfAttendees;
    private boolean vatIdAvailable;
    
    //...

}


[Registration.java from https://github.com/AdamBien/javaee-bce-archetype]

With the introduction of Java API for JSON Processing, you can also directly serialize parts of your objects into JSON:


@Path("health")
@Produces(MediaType.APPLICATION_JSON)
public class HealthResource {

    @Inject
    ServerWatch watch;


    @GET
    @Path("/current-memory")
    public JsonObject availableHeap() {
 JsonObjectBuilder builder = Json.createObjectBuilder();
	builder.add("Available memory in mb", this.watch.availableMemoryInMB()).
	add("Used memory in mb", this.watch.usedMemoryInMb());
	return builder.build();
    }
    
    //...
}


[HealthResource.java from project ping]



Both approaches transport the data without any binary coupling to the origin object. The decoupling is even higher, as it was the case with the "traditional" (=code duplication) DTO implementation.


[See also an in-depth discussion in the "Real World Java EE Night Hacks--Dissecting the Business Tier" book, page 273 in, chapter "Data Transfer Object"]



See you at Java EE Workshops at MUC Airport or on demand and in a location very near you: airhacks.io!