ExampleEntity.scala

import javax.persistence._
import org.eclipse.persistence.annotations.Converter
import org.eclipse.persistence.annotations.Convert

class Entity {
  @Column(nullable=false, updatable=false)
  @Converter(name="jodadatetime", converterClass=classOf[JodaTimeConverter])
  @Convert("jodadatetime")
  var created: org.joda.time.DateTime = _
}

JodaTimeConverter.java

import org.eclipse.persistence.mappings.DatabaseMapping;
import org.eclipse.persistence.mappings.converters.Converter;
import org.eclipse.persistence.sessions.Session;
import org.joda.time.DateTime;
import java.sql.Timestamp;

public class JodaTimeConverter implements Converter {
	private static final long serialVersionUID = 1L;

	public Object convertDataValueToObjectValue(Object dataValue,
			Session session) {
		Timestamp value = (Timestamp) dataValue;
		return new DateTime(value);
	}

	public Object convertObjectValueToDataValue(Object objectValue,
			Session session) {
		DateTime value = (DateTime) objectValue;
		return new Timestamp(value.getMillis());
	}

	public void initialize(DatabaseMapping mapping, Session session) {
	}

	public boolean isMutable() {
		return false;
	}

}