hibernate的Criteria作连表查询

Hibernater中，用Criteria作查询，如果所查询的对象PO中的属性也有一个对象PO，而且要把这个属性PO里的某个属性作为一个查询条件，则必须先为这个属性PO起一个别名！例子如下所示：有一产品表product与一产品类型表type，对应的PO为Product.java、Type.java,对应的映射文件为：Product.hbm.xml、Type.hbm.xml,映射文件如下：
<?xml version="1.0" encoding="utf-8"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN""http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"><!-- Mapping file autogenerated by MyEclipse Persistence Tools--><hibernate-mapping> <class name="com.qhit.po.Product" table="product" catalog="test"> <id name="pid" type="integer"> <column name="pid" /> <generator class="native" /> </id> <many-to-one name="type" class="com.qhit.po.Type" lazy="false" > <column name="typeid" /> </many-to-one> <property name="pname" type="string"> <column name="pname" length="50" not-null="true" /> </property> </class></hibernate-mapping>
<?xml version="1.0" encoding="utf-8"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN""http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"><!-- Mapping file autogenerated by MyEclipse Persistence Tools--><hibernate-mapping> <class name="com.qhit.po.Type" table="type" catalog="test"> <id name="typeid" type="integer"> <column name="typeid" /> <generator class="native" /> </id> <property name="typename" type="string"> <column name="typename" length="50" not-null="true" /> </property> <set name="products" inverse="true" cascade="save-update"> <key> <column name="typeid" /> </key> <one-to-many class="com.qhit.po.Product" /> </set> </class></hibernate-mapping>
查询的例子如下所示：
Session session = HibernateSessionFactory.getSession(); Criteria cri = session.createCriteria(Product.class); cri.createAlias("type", "b"); cri.add(Restrictions.eq("pid", 2)); cri.add(Restrictions.like("pname", "%香%")); cri.add(Restrictions.eq("b.typeid", 2)); cri.add(Restrictions.eq("b.typename", "水果")); List list = cri.list(); for(int i=0;i<list.size();i++){ Product p = (Product)list.get(i); System.out.println("pid = " + p.getPid() + ":pname = " + p.getPname() + ":typeid = " + p.getType().getTypeid() + ":typename" + p.getType().getTypename()); } session.close();