How to get Hibernate dialect during runtime

问题:

In my application, I use Hibernate with SQL Server database, so I set

<property name="hibernate.dialect" value="org.hibernate.dialect.SQLServerDialect">

in my persistence.xml.

In some case, I want to sort records with NULL include, I use keyword NULLS FIRST.
Because it is not supported by default by CriteriaQuery/CriteriaBuilder in Hibernate, then I use Interceptor to modify the native query.
The problem is, keyword NULLS FIRST is not supported in SQL Server, so I use keyword:

case when column_name is null then 0 else 1 end, column_name

If I want to migrate database from SQL Server to Oracle (for example), then I need to put if-else in my Interceptor, choosing which dialect I am using, right?

This is how I illustrate them:

String dialect = ..............
if (dialect.equals("org.hibernate.dialect.SQLServerDialect")) { // get SQL Server dialect
     // put keyword "case when column_name is null then 0 else 1 end, column_name"
} else {
     // put keyword "NULLS FIRST/LAST"
}

How I can get the dialect configuration (in persistence.xml) during runtime?

回答1:

If you use Spring+hibernate, try this

@Autowired@Qualifier("sessionFactory") org.springframework.orm.hibernate3.LocalSessionFactoryBean sessionFactory; //Suppose using hibernate 3

and in your method:

sessionFactory.getHibernateProperties().get("hibernate.dialect")

回答2:

I have found the answer from this post : Resolve SQL dialect using hibernate

Thank you for @Dewfy,

here is the solution:

//take from current EntityManager current DB Session
Session session = (Session) em.getDelegate();
//Hibernate's SessionFactoryImpl has property 'getDialect', to
//access this I'm using property accessor:
Object dialect = 
       org.apache.commons.beanutils.PropertyUtils.getProperty(
          session.getSessionFactory(), "dialect");
//now this object can be casted to readable string:
if (dialect.toString().equals("org.hibernate.dialect.SQLServerDialect")) {

} else {

}

回答3:

The following works well for me for accessing the dialect in a Java EE application running in WildFly 14:

import org.hibernate.Session;
import org.hibernate.dialect.Dialect;
import org.hibernate.internal.SessionFactoryImpl;

...

@PersistenceContext
private EntityManager entityManager;

...

final Session session = (Session) entityManager.getDelegate();
final SessionFactoryImpl sessionFactory = (SessionFactoryImpl) session.getSessionFactory();
final Dialect dialect = sessionFactory.getJdbcServices().getDialect();
logger.info("Dialect: {}", dialect);

You need to add hibernate-core dependency with provided scope to pom.xml.