Hi Ted - A few more questions to fill out my knowledge -
How does your original example of ManyToMany annotation on a Collection
of Enums actually work? My understanding is that for ManyToMany both
sides must be persistent Entities. So therefore the ManyToMany is
mapping the join table, not the Enum.
Isn't the same thing true that OneToMany should annotate a Collection of
Entities? So the Enums would be a field on the ManyToOne side of that
kind of mapping. Then you can specify the @Column and @Enumerated
annotations on the actual field or property.
Could you explain why using the @PersistentCollection annotation is
useful or necessary for OneToMany or ManyToMany collections generally or
specifically in the case you are looking at? I don't understand the use
case that @PersistentCollection satisfies.
- Paul
On 3/29/2009 8:43 PM, Tedman Leung wrote:
Just to document more thoughts and findings.
1) I was using the wrong annotation, I should have been using
@PersistentCollection
2) this seems to be a more wide spread problem with defining
attributes to collections, i.e.
- collection of enums needs to have @Enumerated configurations
- collection of Dates needs to have @Temporal configurations
- even collection of Strings seems to be missing a
@Column(nullable=false, length=32) style annotation.
I think the problem is much bigger and wide spread than I originaly though,
I don't think I'll be able to sort out a patch.
On Sun, Mar 29, 2009 at 07:55:06AM -0700, Tedman Leung wrote:
yes I know I can do manual hacks to get them stored the way I want to, but
I was asking if there was a jpa / openjpa annotation to allow that.
As an example, I can just use @Enumerated on a single enum, so it seems
logical that some one would have thought about storing a collection of
enums.
As for why I want them as strings instead of ordinals - the usual reasons,
i.e. it's safer for changes as the ordering won't accidentally corrupt my
data (and without telling me), and it's easier to look into the database
via sql or something and just know what's going on / get simple reports
etc.
I'm guessing right now that it's not possible at all and that no one has
done anything towards this. I might have to rummage through the source
and try to see if I can figure out how it works and hack a patch to
submit. It seemed like a very straight forward use case though so I'm
surprised no one has asked or done anything about this before.
On Sat, Mar 28, 2009 at 10:13:16PM -0700, Paul Copeland wrote:
What is your objective? Do you want some non-JPA application to see
them in the database as Strings?
At some point you have add these Enums to the collection one at a time.
You can use an addEnum() method or an Entity listener to convert them to
Strings at that point one at a time. And a subclass of the Collection
type to getEnum() from the Collection when you fetch them back.
new MyStringEnumHashSet<MyStringEnumType>()
On 3/28/2009 9:27 PM, Tedman Leung wrote:
No, I'm talking about when the enum is in a collection.
i.e.
Private HashSet<Gender> genders=new HashSet<Gender>();
So no, either the @Enumerated helps, nor does calling name() or
toString as neither are possible.
I'm storing a Collection of enums , not a single Enum.
There seems to be no examples of this nor any documentation about the
ability to do this that I can find. The default seems to use the
ordinal value both for table generation and storage value.
On Sat, Mar 28, 2009 at 01:56:13PM -0700, Paul Copeland wrote:
Hi - This is from the OpenJPA relations example -
@Basic @Enumerated(EnumType.STRING)
private Gender gender;
public static enum Gender { MALE, FEMALE }
public void setGender(Gender gender) {
this.gender = gender;
}
See section 12.8.1.2 in the OpenJPA Overview
- Paul
On 3/28/2009 1:33 PM, catalina wei wrote:
Ted,
If you are using Java 5, then you could use name() or toString() API on the
Enum to get the name of the enum constant in String value.
Catalina
On Wed, Mar 25, 2009 at 9:48 AM, Tedman Leung <ted...@sfu.ca> wrote:
Anyone know how to store a collection of enums as Strings instead of their
ordinal values? (preferably with annotations...)
i.e.
@ManyToMany
private Set<MyEnum> myEnums=new HashSet<MyEnum>();
--
Ted Leung
ted...@sfu.ca
It's time for a new bike when the bulb in your shift light burns out.
--
Ted Leung
ted...@sfu.ca
The most important words I've learned to say - "I don't know".
