Criteria API 学习

package myHibernate;

import java.util.Iterator;
import java.util.List;

import org.hibernate.Criteria;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.hibernate.criterion.Criterion;
import org.hibernate.criterion.DetachedCriteria;
import org.hibernate.criterion.Disjunction;
import org.hibernate.criterion.LogicalExpression;
import org.hibernate.criterion.Property;
import org.hibernate.criterion.Restrictions;

import junit.framework.TestCase;

public class CriteriaAPITest extends TestCase {
 
 public void testCriteria() {
  Session session = null;
  Transaction tx = null;
  try {
   session = HibernateUtils.getSession();
   tx = session.beginTransaction();
   //使用Criteria API进行查询
   Criteria crit = session.createCriteria(Student.class);
   //查询名字不等于小桂的学生
  // crit.add(Restrictions.ne("name", "小桂"));
   
   //查询名字为校规的学生
  // crit.add(Restrictions.eq("name", "校规"));
   
   //查询名字由余开头的学生
  // crit.add(Restrictions.like("name", "余%"));
   
   //查询id<2的学生
  // crit.add(Restrictions.lt("id", new Integer(2)));
   
   //查询id>2的学生
   //crit.add(Restrictions.gt("id", new Integer(2)));
   
   //查询id>2并且（and）名称以规结尾的学生,注意：添加多个限制时，解释为and关系
   //hibernate发错的sql语句为：
   //Hibernate: select this_.id as id1_0_, this_.name as name1_0_, this_.createTime
   //as createTime1_0_, this_.classid as classid1_0_ from Student this_ where this_.id>? and this_.name like ?
  /*crit.add(Restrictions.gt("id", new Integer(2)));
   * crit.add(Restrictions.like("name", "%规"));
   * */ 
   
   //如果只是想满足两个条件中某一个条件(or)，就需要使用Restrictions类上的or（）方法，如下所示：
   //Criterion定义一个条件项
/*   Criterion id = Restrictions.gt("id", new Integer(2));
   Criterion name = Restrictions.like("name", "%规");
   LogicalExpression orExp = Restrictions.or(id, name);
   crit.add(orExp);*/
   
/*   如果要创建多于两个的or表达式，则可以使用org.hibernate.criterion.Disjuncion对象来表示析取(disjunction)
   从Restrictions类上的disjunction()工厂方法获得这个对象。
   要创建多于2个的AND表达式，可以使用conjunction()方法（合取）*/

   Criterion name = Restrictions.like("name", "%规");
   Criterion name1 = Restrictions.like("name", "%成");
   Criterion name2 = Restrictions.like("name", "余%");
   Disjunction disjunction = Restrictions.disjunction();
   disjunction.add(name);
   disjunction.add(name1);
   disjunction.add(name2);
   crit.add(disjunction);
   List results = crit.list();
   Iterator iter = results.iterator();
   while(iter.hasNext()){
    Student s = (Student)iter.next();
    System.out.println(s.getName());
   }
   
   tx.commit();
  } catch (HibernateException e) {
   e.printStackTrace();
   if (tx != null)
    tx.rollback();
  } finally {
   HibernateUtils.closeSession(session);
  }
 }
 
 public void testCriteria2() {
  Session session = null;
  Transaction tx = null;
  try {
   session = HibernateUtils.getSession();
   tx = session.beginTransaction();
   Criteria crit = session.createCriteria(Student.class);
   //创建一个别名
   Criteria classCriteria = crit.createAlias("classes", "c");
   crit.setProjection(Property.forName("name"));
   Criterion name = Restrictions.like("c.name", "714");
   crit.add(name);
   List results = crit.list();
   Iterator iter = results.iterator();
   while(iter.hasNext()){
    System.out.println(iter.next());
   }
/*   while(iter.hasNext()){
    Student s = (Student)iter.next();
    System.out.println(s.getName());
   }*/
   
   tx.commit();
  } catch (HibernateException e) {
   e.printStackTrace();
   if (tx != null)
    tx.rollback();
  } finally {
   HibernateUtils.closeSession(session);
  }
 }
}

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