Using @ElementCollection to persist a Collection of Enum

[roberto_sc]

I'm moving from JPA 1 to JPA 2 in my Gooogle App Engine project, and for that I changed the annotations for collections of enums, like this case:

//  @OneToMany(cascade = CascadeType.ALL) // JPA 1
    @ElementCollection(targetClass=PositioningType.class)
    private List<PositioningType> bestPositionings;




PositioningType is an enum that is not annotated.

That code is giving me the following exception:

javax.persistence.PersistenceException: The MetaData for the element class "com.olympya.datamodel.model.PositioningType" of the collection field "com.olympya.datamodel.model.Player.bestPositionings" was not found.
at org.datanucleus.api.jpa.NucleusJPAHelper.getJPAExceptionForNucleusException(NucleusJPAHelper.java:302)
at org.datanucleus.api.jpa.JPAEntityTransaction.commit(JPAEntityTransaction.java:122)
at com.olympya.Services.mergeUser(Services.java:102)
...
Caused by: org.datanucleus.exceptions.NucleusUserException: The MetaData for the element class "com.olympya.datamodel.model.PositioningType" of the collection field "com.olympya.datamodel.model.Player.bestPositionings" was not found.
at com.google.appengine.datanucleus.scostore.AbstractFKStore.<init>(AbstractFKStore.java:120)
at com.google.appengine.datanucleus.scostore.FKListStore.<init>(FKListStore.java:83)
at com.google.appengine.datanucleus.DatastoreManager.newFKListStore(DatastoreManager.java:472)
at org.datanucleus.store.mapped.MappedStoreManager.getBackingStoreForCollection(MappedStoreManager.java:798)
at org.datanucleus.store.mapped.MappedStoreManager.getBackingStoreForField(MappedStoreManager.java:709)
at org.datanucleus.store.types.sco.backed.ArrayList.<init>(ArrayList.java:99)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
...

[roberto_sc]

No opinions at all? Does it look like that I'm doing the right thing?
I just found out that it also doesn't work for a list of integers, possibly any collection of any simple type:

@ElementCollection
@Extension(vendorName = "datanucleus", key = "gae.unindexed", value = "true")
//private List<PositioningType> bestPositionings = new ArrayList<PositioningType>();
private List<Integer> bestPositionings;

Results in:

Caused by: org.datanucleus.exceptions.NucleusUserException: The MetaData for the element class "java.lang.Integer" of the collection field "com.olympya.datamodel.model.Player.bestPositionings" was not found.

at com.google.appengine.datanucleus.scostore.AbstractFKStore.<init>(AbstractFKStore.java:120)
at com.google.appengine.datanucleus.scostore.FKListStore.<init>(FKListStore.java:83)
at com.google.appengine.datanucleus.DatastoreManager.newFKListStore(DatastoreManager.java:472)
at org.datanucleus.store.mapped.MappedStoreManager.getBackingStoreForCollection(MappedStoreManager.java:798)
at org.datanucleus.store.mapped.MappedStoreManager.getBackingStoreForField(MappedStoreManager.java:709)
at org.datanucleus.store.types.sco.backed.ArrayList.<init>(ArrayList.java:99)

:(

[Eduardo Perrino]

Hi Roberto,

@ElementCollection annotation have to be used to contain embedded entities, therefore you're have to be sure that PositioningType class is annotated with @Embeddable. 

 The next example works fine for me:

//Class Product

@ElementCollection(fetch = FetchType.EAGER)

 public Set<Rate> rates;

//Class Rate

@Embeddable

public class Rate {

   public String name;

}

Regards.

2012/8/30 roberto_sc <roberto...@gmail.com>

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[Roberto Caldas]

Hello Eduardo

No, the documentation states that it can be used for simple types also: "Defines a collection of instances of a basic type or embeddable class" (http://docs.oracle.com/javaee/6/api/javax/persistence/ElementCollection.html).

This 2 links points that ElementCollection should be used with enums:
http://docs.oracle.com/javaee/6/api/javax/persistence/Enumerated.html
http://stackoverflow.com/questions/416208/jpa-map-collection-of-enums