How do I drop a database or collection using Hibernate OGM with MongoDB

Question

I can't drop databases or collections using Hibernate OGM. I've tried using these native queries but an exception is thrown for both

entityManagerFactory = Persistence.createEntityManagerFactory("myPersistence-unit");
EntityManager entityManager = openEntityManager( entityManagerFactory);
entityManager.getTransaction().begin();

    String queryDropCollection = "db.Person.drop()";
    String queryDropDB = "db.dropDatabase()";

    entityManager.createNativeQuery(queryDropCollection).executeUpdate();
    entityManager.createNativeQuery(queryDropDB).executeUpdate();

entityManager.getTransaction().commit();
entityManager.close();

The exception for dropping the collection:

Exception in thread "main" com.mongodb.util.JSONParseException: 
db.Person.drop()
^

The exception for dropping the database:

Exception in thread "main" com.mongodb.util.JSONParseException: 
db.dropDatabase()
^

Answer 1

Sorry, this is not possible right now.

I'm not sure if it would be a good idea to drop the database while OGM is using it, though.

I've created these two issues to keep track from it:

• Drop db: https://hibernate.atlassian.net/browse/OGM-1432
• Drop collection: https://hibernate.atlassian.net/browse/OGM-1433

Thanks for the feedback. If you feel like trying to help us even more, you could try to solve the issues in the project and send us a fix. We will help you.

Answer 2

So, just to give a concrete example of how to use this in tests, I am adding this answer.

My working repeatable test class using OGM and MongoDB looks like this:

class OgmAccessorTest {

    private static EntityManagerFactory entityManagerFactory;
    private static EntityManager entityManager;
    private static TransactionManager transactionManager;

    @BeforeAll
    static void initialize() {
        entityManagerFactory = Persistence.createEntityManagerFactory("ogm-mongodb");
        entityManager = entityManagerFactory.createEntityManager();
        transactionManager = com.arjuna.ats.jta.TransactionManager.transactionManager();
    }

    @BeforeEach
    void clearDatabase() throws NotSupportedException, SystemException, SecurityException, IllegalStateException, RollbackException, HeuristicMixedException, HeuristicRollbackException {
        transactionManager.begin();
  // Collection == name of the class being saved ⮧
        entityManager.createNativeQuery("db.GameCharacter.drop()").executeUpdate();
        transactionManager.commit();
    }

    @Test
    void writeShouldBeAbleToWriteRetreivableGameCharacterToMongoDB() throws SecurityException, IllegalStateException, NotSupportedException, SystemException, HeuristicMixedException, HeuristicRollbackException, RollbackException {

        GameCharacter sylvia = GameCharacters.sylvia();

        OgmAccessor.write(sylvia, entityManagerFactory);

        transactionManager.begin();
        GameCharacter loadedGameCharacter
            = entityManager.find(GameCharacter.class, sylvia._id);

        assertNotNull(loadedGameCharacter);
    }
}