Using hibernate 2.1 attached to PostgreSQL 7.4.5, I'm havig trouble getting the current time back from the database using hibernate.

My code:

public static java.util.Date getDbCurrentTime() throws
HibernateException
{
Query query = session.createSQLQuery("select CURRENT_TIMESTAMP", "date", java.util.Date.class);
java.util.Date dbTime = (java.util.Date)query.uniqueResult();
log.debug("getDbCurrentTime(): " + dbTime);
return dbTime;
}

When I run this, it fails with an exception
net.sf.hibernate.MappingException: No persister for: java.util.Date
at net.sf.hibernate.impl.SessionFactoryImpl.getPersister(SessionFactoryImpl.java:347)
at net.sf.hibernate.impl.SessionImpl.getClassPersister(SessionImpl.java:2690)
at net.sf.hibernate.impl.SessionImpl.getSQLLoadable(SessionImpl.java:3817)
at net.sf.hibernate.impl.SessionImpl.findBySQL(SessionImpl.java:3796)
at net.sf.hibernate.impl.SQLQueryImpl.list(SQLQueryImpl.java:52)
at net.sf.hibernate.impl.AbstractQueryImpl.uniqueResult(AbstractQueryImpl.java:550)
at com.whatever.DataStore.getDbCurrentTime(DataStore.java:60)

I'm not sure how I would set up a mapper for this since it's not grabbing anything from a table. And besides, doesn't hibernate already know how to map a Date object?

In most cases you won't get a java.util.Date but a java.sql.Date instances (as per the JDBC specs)...

createSQL query can only return Hibernate mapped classes.

So then what can I do to get the current date back from the database using hibernate?

No, Michael said SQL queries... not HQL queries ;)

Unfortunately, it doesn't work with HQL either. Running a query created with session.createQuery("select CURRENT_TIMESTAMP"); causes hibernate to generate and run the SQL query "select CURRENT_TIMESTAMP as x0_0_ from", which naturally doesn't work.

I don't really care about what mechanism I use to do it; I just want to get the current time from the database. Does anyone know how to do this?

session.connection().prepareStatement("select current_timestamp").executeQuery();

Ah thanks. that did the trick.