Prevent Hibernate from generating identity sometimes

shalom · **Joined:** Mon May 28, 2007 4:20 am **Posts:** 6

I am usingHibernate version: 3.3.1 (Annotations 3.2.2)

I have classes that are stored on a server database (MySQL). These classes are serialized and sent to a client, where they are to be put into a local database (Derby 10.2.2.0).

The classes contain annotations for generating an identity column. However on the client, the identity value has to be the same as on the server. When I add the received objects, Hibernate generates a new ID value, and (of course) throws an exception if I try to change it later.

Code:

   @Id
   @GeneratedValue(strategy=GenerationType.AUTO)
   @Column(name = "ID", nullable = false)
   private Integer id = null;

What I need is a way of overriding the annotation on the client, or forcing Hibernate to accept the incoming ID. I would like to use JPA standard things only because sometimes I have to use these classes with other frameworks (like Toplink).

There is a way out - if I can't find anything else - and that is to generate the ID's myself when new records are inserted on the server (and remove the @GeneratedValue). However I prefer not to do this if possible.

shalom · **Joined:** Mon May 28, 2007 4:20 am **Posts:** 6

I may just have solved this problem, though I'd still appreciate any feedback.

On the client (only) I added an orm.xml file that overrides the definition of the ID field only. (I have removed identifiers, and replaced them with '....')

This seems to do what's necessary - preventing Hibernate from generating an ID for this field - only on the client. I didn't add definitions for the other fields in the class.

Code:

<?xml version="1.0" encoding="UTF-8" ?>
<entity-mappings xmlns="http://java.sun.com/xml/ns/persistence/orm"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm http://java.sun.com/xml/ns/persistence/orm_1_0.xsd"
    version="1.0">
    <package>......</package>
    <entity class="....." name="....">
        <attributes>
            <id name="id">
               <column name="ID" />
            </id>
        </attributes>
    </entity>
</entity-mappings>

emmanuel · **Posted:** Tue May 29, 2007 2:57 pm

session.replicate might be interesting as well