Generate ObjectId values for _id in Mongo

registration_pain · **Joined:** Mon Mar 24, 2014 1:10 am **Posts:** 3

How to accoumplish subj?
Nothing about strategies in documentation.
@GeneratedValue(generator = "native") doesn't work.

DavideD · **Joined:** Fri Sep 09, 2011 3:18 am **Posts:** 295

Hi,
these generation strategies should work:

Code:

@Entity
public class Helicopter {
      ...
@Id
@GeneratedValue(generator = "uuid")
@GenericGenerator(name = "uuid", strategy = "uuid2")
   public String getId() {
      return uuid;
   }
...
}

or

Code:

@Entity
public class Helicopter {

...
   @Id
   @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "helicopter_seq")
   @SequenceGenerator(name = "helicopter_seq")
   public Integer getId() {
      return id;
   }
...
}

or

Code:

@Entity
public class Helicopter {

...
   @Id
   @GeneratedValue(strategy = GenerationType.AUTO)
   public Long getId() {
      return id;
   }
..
}

registration_pain · **Joined:** Mon Mar 24, 2014 1:10 am **Posts:** 3

They work, but don't do the thing.
Consider ObjectId

Quote:

ObjectId is a 12-byte BSON type, constructed using:

a 4-byte value representing the seconds since the Unix epoch,
a 3-byte machine identifier,
a 2-byte process id, and
a 3-byte counter, starting with a random value.

versus uuid

Quote:

uuid
Generates a 128-bit UUID based on a custom algorithm. The value generated is represented as a string of 32 hexidecimal digits. Users can also configure it to use a separator (config parameter "separator") which separates the hexidecimal digits into 8{sep}8{sep}4{sep}8{sep}4. Note specifically that this is different than the IETF RFC 4122 representation of 8-4-4-4-12.

As for two other options here is another quote from mongodb.org

Quote:

WARNING
Generally in MongoDB, you would not use an auto-increment pattern for the _id field, or any field, because it does not scale for databases with large numbers of documents. Typically the default value ObjectId is more ideal for the _id.

DavideD · **Joined:** Fri Sep 09, 2011 3:18 am **Posts:** 295

Good point,
at the moment is not possible to use the mongodb generated ObjectId.

Gunnar · **Joined:** Sat Jan 24, 2009 12:46 pm **Posts:** 388

I've created https://hibernate.atlassian.net/browse/OGM-526 to track this requirement. Definitely something we should support some time soon.

--Gunnar

DavideD · **Joined:** Fri Sep 09, 2011 3:18 am **Posts:** 295

Hibernate OGM now supports this feature: http://in.relation.to/Bloggers/MongoDBObjectIdSupportAndRestructuredPublicAPIHibernateOGM410Beta7IsOut