Configuration of two Mongo databases

Hibernate OGM
1

Hi,

I want to configure two mongo databases. how can I define it in the Persistence.xml file?

2

You need to create two distinct persistence units for this case:


<persistence ...>
    <persistence-unit name="mongoPU-1" transaction-type="JTA">
        <provider>org.hibernate.ogm.jpa.HibernateOgmPersistence</provider>
        <properties>
            ...
        </properties>
    </persistence-unit>
    <persistence-unit name="mongoPU-2" transaction-type="JTA">
        <provider>org.hibernate.ogm.jpa.HibernateOgmPersistence</provider>        
        <properties>
            ...
        </properties>
    </persistence-unit>
</persistence>

Then in your code you can access the one you need with the annotation:

@PersistenceUnit(uniteName="mongoPU-2")
EntityManagerFactory ef;

or

EntityManagerFactory emf = Persistence.createEntityManagerFactory( "mongoPU-1 );

Note that they are two distinct persistence units and you cannot, for example, have a join on two entities that are not in the same factory.

I hope this help.

3

thank you for your quick response. this works perfectly in my project but now i have another issue in my project i have a some object variables, when i want to perform a query it gives me the error that type is wrong.

e.g
private object environment;
private object extension;

unders these object i also some nested object, should i have to perform this query in native language or i can also use JPQL?

4

Hibernat OGM doesn’t know how to convert the object and that’s why you see an error.
Supported built-in type are here: https://docs.jboss.org/hibernate/stable/ogm/reference/en-US/html_single/#mongodb-built-in-types

You could use a native query but a better solution would be to change the mapping of your entities using the appropriate type. If the document are nested you can map them as embedded entities: https://docs.jboss.org/hibernate/stable/ogm/reference/en-US/html_single/#_embedded_objects_and_collections_2

One example from the documentation:



@Entity
public class News {

    @Id
    private String id;
    private String title;

    @Embedded
    private NewsPaper paper;

    // getters, setters ...
}

@Embeddable
public class NewsPaper {

    private String name;
    private String owner;

    // getters, setters ...
}
5

i have a one more question, is this modle also work with SQL or it is only for NoSQL databases?

6

Yes, that’s the idea around Hibernate OGM.

If you use the JPA annotations and JPQL it doesn’t matter which datastore you are using (in theory).

Moving from a nosql datastore to a relational one, should work fine.

1 Like
7

Thank you very much for your help.