Java hibernate如何使用Projections计算总记录？
以下示例显示了如何使用来获取总行数Projections.rowCount()。该查询的结果将是一个对象，Integer其中包含执行SQL选择计数（*）命令的结果。
package org.nhooo.example.hibernate.criteria;
import org.hibernate.SessionFactory;
import org.hibernate.Session;
import org.hibernate.HibernateException;
import org.hibernate.Criteria;
import org.hibernate.cfg.Configuration;
import org.hibernate.criterion.Projections;
import org.nhooo.example.hibernate.model.Track;
import java.util.List;
public class ProjectionsCountDemo {
public static Session getSession() throws HibernateException {
String cfg = "hibernate.cfg.xml";
SessionFactory sessionFactory = new Configuration().configure(cfg)
.buildSessionFactory();
return sessionFactory.openSession();
}
@SuppressWarnings("unchecked")
public static void main(String[] args) {
try (Session session = getSession()) {
Criteria criteria = session.createCriteria(Track.class)
.setProjection(Projections.rowCount());
List result = criteria.list();
if (!result.isEmpty()) {
Long rowCount = (Long) result.get(0);
System.out.println("Total records: " + rowCount);
}
}
}
}