Hibernate Mapping for Collection<Enum> ?

rody · **Joined:** Mon Feb 28, 2005 10:39 am **Posts:** 1

Hibernate version:
3.0beta3

Hello,

I was wondering how I can map a one-to-many relationship with a Collection<Enum> on the many side.

for example, I have a User class:

Code:

@Entity
public class User {
    private String username;
    private String password;
    private Set<Role> roles;

   // getters and setters...

    public final Set<Role> getRoles() {
        return this.roles;
    }

    public final void setRoles(Set<Role> roles) {
        this.roles = roles;
    }
}

and a Role enumeration like this :

Code:

public enum Role {
    ADMINISTRATOR, MODERATOR, USER;
}

I use a custom RoleUserType to persist Role (see "UserType for persisting an Enum with a VARCHAR column" at http://www.hibernate.org/265.html).

Thanks.

PS: I'd like to use annotations as much as I can, so if you know how to do this with annotations...

gavin · **Posted:** Mon Feb 28, 2005 12:21 pm

Should be easy. A collection of values may use a UserType as the element type.

ivaynberg · **Joined:** Mon Oct 11, 2004 11:29 am **Posts:** 11

Any way to do this using ejb3 annotations?

Code:

@OneToMany(targetEntity=Enum.class) Set<SomeEnum> getFoo()

gives

Code:

org.hibernate.MappingException: Association references unmapped class: java.lang.Enum

and

Code:

@OneToMany Set<SomeEnum> getFoo()

gives

Code:

Association references unmapped class: <enum class>

Thanks!

emmanuel · **Posted:** Fri Jul 22, 2005 1:07 pm

Collections of primitive types are not supported yet, sorry.

ivaynberg · **Joined:** Mon Oct 11, 2004 11:29 am **Posts:** 11

Is this a limitation of hibernate or ebj3 spec?

emmanuel · **Posted:** Fri Jul 22, 2005 1:12 pm

This will not be part of the spec, and Hibernate will provide this feature as a specific extension.

ivaynberg · **Joined:** Mon Oct 11, 2004 11:29 am **Posts:** 11

Are there any suggested work arounds that will stay within the ejb3 spec?

emmanuel · **Posted:** Fri Jul 22, 2005 1:15 pm

public class MyEnumedEntity {
@Id public Integer getId() ...
public Enum getEnum() ...
}

ivaynberg · **Joined:** Mon Oct 11, 2004 11:29 am **Posts:** 11

First let me say thanks for all the help emmanuel.

If I use MyEnumEntity it will be mapped to its own table correct? So I will have three tables instead of two.

Also, using previous example my model will contain Set<MyEnumEntity> and not Set<Role> correct? This I think can be fixed with interceptors to sync between the two.

Are my assumptions correct?

I am really trying to avoid having another table in the database though.

Thanks!

emmanuel · **Posted:** Fri Jul 22, 2005 2:15 pm

why 3 tables?

User
MyEntityEnum

instead of
User
EnumTable

If you don't want any extra table you could probably write a usertype serializing your enums ( ENUM1, ENUM2 ) in 1 column

ivaynberg · **Joined:** Mon Oct 11, 2004 11:29 am **Posts:** 11

Maybe I am missing something...
If I map MyEntityEnum as an entity wont my tables look like this?

[User id, firstname, lastname, foo]
[UserEntityLink userId, enumId]
[MyEntityEnum id]

When I was using hibernate instead of ejb3 I used a type that mapped the enum to a varchar so I would only have the top two tables.

emmanuel · **Posted:** Fri Jul 22, 2005 3:43 pm

The assoc table is unnecessary for a OneToMany association.

ivaynberg · **Joined:** Mon Oct 11, 2004 11:29 am **Posts:** 11

Ohhh daah, I was looking at it the wrong way.

emmanuel wrote:

public class MyEnumedEntity {
@Id public Integer getId() ...
public Enum getEnum() ...
}

Here you meant the id is referring to the user's id not some arbitrary enum id. Get it now. Thanks!

I wonder why the ejb3 spec doesnt support such a common usecase.

Thanks a lot!

emmanuel · **Posted:** Fri Jul 22, 2005 4:04 pm

no id is refering to an arbitrary id, but the userid will be in the table tnaks to

@OneToMany
@joinColumn(name="userId")
Set...

This kind of case may be common in small apps, but not in EE apps

ivaynberg · **Joined:** Mon Oct 11, 2004 11:29 am **Posts:** 11

Sorry to waste your time Emmanuel. Ive been head deep into jboss xml files all morning and my head is not in the right place. I see what you are saying now.

Do you see any clean way to keep the model clean. I was thinking a set decorator that can dynamically convert from the enum wrapper into the enum. Not sure how feasible that is until I try it. What do you think?

Quote:

This kind of case may be common in small apps, but not in EE apps

I meant the Collection<Enum> not the user/role deal.

Thanks!