Hi,
I have an intermittent problem using MapKey.

The tables and data already exist, so I don't have much freedom on changing them, and I am trying to find a way to map them with Hibernate annotations.
Let say that I have two tables PERSON and FAVORITE_COLOR (these are not the actual tables, just trying to simplify with a similar example):
PERSON
FAMILY_ID
NAME
HEIGHT

FAVORITE_COLOR
FAMILY_ID
PERSON_NAME
OBJECT_TYPE
FIRST_COLOR_CHOICE
SECOND_COLOR_CHOICE

PERSON primary index is based on (FAMILY_ID, NAME).

The second table stores the two favorites color of a person. There is uniqueness on (FAMILY_ID, PERSON_NAME, OBJECT_TYPE). FAMILY_ID and PERSON_NAME just come from PERSON. OBJECT_TYPE describes the favorite color for a particular object, for example "shirt", "house", "car" .. So a person can have different choices for different object. OBJECT_TYPE can be NULL, in this case the colors are the person favorite colors regardless of any particular object.

So I created the following annotations (I ommited what I think is irrelevant):

@Entity
@Table(name = "PERSON")
@IdClass(Person.PersonPk.class)
public class Person {
... @Id and other properties ...

@OneToMany(cascade=CascadeType.ALL, fetch = FetchType.EAGER)
@MapKey(name = "object")
@JoinColumns({
@JoinColumn(name = "FAMILY_ID", updatable=false, referencedColumnName = "FAMILY_ID"),
@JoinColumn(name = "PERSON_NAME", updatable=false, referencedColumnName = "NAME")
})
@AttributeOverrides({
@AttributeOverride(name = "object", column = @Column(name = "OBJECT_TYPE", updatable = false, nullable = true))
})
private Map<String, FavoriteColor> favorites;

...
@Embeddable
public static class PersonPk {
...
}
}
My second entity:

@Entity
@Table(name="FAVORITE_COLOR")
@IdClass(FavoriteColorPk.class)
@AttributeOverrides({
@AttributeOverride(name = "familyId", column = @Column(name = "FAMILY_ID", updatable = false)),
@AttributeOverride(name = "name", column = @Column(name = "PERSON_NAME", updatable = false)),
@AttributeOverride(name = "object", column = @Column(name = "OBJECT_TYPE", updatable = false, nullable = true))
})
public class FavoriteColor {

@Id long familyId;
@Id String name;
@Id String object;

@Column(name="FIRST_COLOR_CHOICE")
String firstColorChoice;

@Column(name="SECOND_COLOR_CHOICE")
String secondColorChoice;

... (getters and setters) ...
String getObject() {
return object;
}

@Embeddable
public static class FavoriteColorPk {
... properties of the key...
}
}

As long as I insert favorite colors associated with an object (not NULL), everything works fine.
But I start to get intermittent errors when I insert favorite colors for no object (OBJECT_TYPE=null).
The error I get is:

[04-08 14:06:04] INFO DefaultLoadEventListener [main]: Error performing load command
org.hibernate.HibernateException: null index column for collection: com.acme.sdk.service.data.Person.favorites

at org.hibernate.persister.collection.AbstractCollectionPersister.readIndex(AbstractCollectionPersister.java:710)
at org.hibernate.collection.PersistentMap.readFrom(PersistentMap.java:258)
at org.hibernate.loader.Loader.readCollectionElement(Loader.java:1008)
at org.hibernate.loader.Loader.readCollectionElements(Loader.java:646)
at org.hibernate.loader.Loader.getRowFromResultSet(Loader.java:591)

a) Is it possible to use @MapKey with a property (in this case "object") that accepts nulls ?

I would assume it is possible since I don't get the error every time. But I may be missing some annotation attribute for it to always work.

b) When I add/remove elements from the map, do I need explicitly call session.saveOrUpdate() on each FavoriteColor ? Is it enough to do a saveOrUpdate(person)?

I was also trying to create the map using the FavoriteColorPk, so that it would never be null, but then I don't know what to use in the attributes of @MapKey.

private Map<FavoriteColorPk, FavoriteColor> favorites;


Help is very much appreciated.

-Jorge

Did you manage to solve this problem, since I am facing the same error?

Thank you in advance