Hibernate loading an object with composite key always returns

Question

here is a snippet of my entity (it also has hashcode and equals created which are the default ones generated by java

@Entity 
@Table(name = "media_tspec_external_registry")
public class Registry implements Serializable {


public Registry() {
    //for hibernate :D
}



public Registry(String show, String protocol, String externalEndpoint, String userURI, String version) {
    super();
    this.show = show;
    this.protocol = protocol;
    this.externalEndpoint = externalEndpoint;
    this.userURI = userURI;
    this.version = version;
}




@Id
@Column(name = "show", nullable = false)
private String show;

@Id
@Column(name = "protocol", nullable = false)
private String protocol;

@Column(name = "external_endpoint", nullable = true)
private String externalEndpoint;

here is my method which is trying to load an entity which does not exist, based on these key values

Registry reg = new Registry("invalid", "idvalue", null, null, null);
    Registry reg2 = null;
    try {

        reg2 = (Registry) session.load(Registry.class, reg);
             } catch (HibernateException e) {
        throw new UserException("A registry entry does not exist for this show: " + show + " and protocol: " + protocol);
        }

it never throws the exception and reg2 is now set to a registry object with all the fields set to null.

i have also noted that the load will not even load a existing entity.

however if i use get instead it works as expected (loading valid object returning null for non existing objects)

reg2 = (Registry) session.get(Registry.class, reg);

any explanation would be appreciated.

Thanks

Strange. Registry is both entity and composite key at the same time? — Piotr Kochański, Apr 25 '12 at 17:58
@PiotrKochański based on the [hibnate docs](http://docs.jboss.org/hibernate/annotations/3.5/reference/en/html_single/#entity-mapping-identifier) section 2.2.3.2.2. i took that to mean that the entity itself was the serializable identifier (similar to an idclass or embedded id) — Shaun Stone, Apr 25 '12 at 18:16
Look at answer to question http://stackoverflow.com/q/608947/971040 It may direct you in the right way. — viktor, Apr 25 '12 at 21:20
@viktor thanks looks like i am seeing a behavior mentioned in that post **specfically Using load() has a further implication: The application may retrieve a valid reference (a proxy) to a persistent instance without hitting the database to retrieve its persistent state. So load() might not throw an exception when it doesn’t find the persistent object in the cache or database; the exception would be thrown later, when the proxy is accessed.** sounds like a bug to me, but at least i have an answer... thanks for you help — Shaun Stone, Apr 25 '12 at 23:37

score 1 · Accepted Answer · answered Apr 26 '12 at 10:04

this is expected behavior. session.load is meant to get an object which can be used to satisfy references, e.g.

User u = new User();
u.setRole((Role)session.load(Role.class, 5));
session.save(u);

load will not generate a roundtrip. If there is no reference to the object available it will create a proxyobject or in your case will recycle your compositekey object and relies on you that the entity exists since it can not ask the database if it is so.

Hibernate loading an object with composite key always returns

1 Answers1