懒加载
通过asm和cglib二个包实现；Domain是非final的。
1.session.load懒加载。
2.one-to-one(元素)懒加载：
必需同时满足下面三个条件时才能实现懒加载
(主表不能有constrained=true,所以主表没有懒加载)
lazy!=false 2)constrained=true 3)fetch=select
3.one-to-many (元素)懒加载：1)lazy!=false 2)fetch=select
4.many-to-one (元素) ：1)lazy!=false 2)fetch=select
5.many-to-many (元素) ：1)lazy!=false 2)fetch=select
6.能够懒加载的对象都是被改写过的代理对象，当相关联的session没有关闭时，访问这些懒加载对象（代理对象）的属性（getId和getClass除外）hibernate会初始化这些代理，或用Hibernate.initialize(proxy)来初始化代理对象；当相关联的session关闭后，再访问懒加载的对象将出现异常。
一对一懒加载（对系统影响不算太大）
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.dzq.domain"> <class name="IDCard" table="id_card">
<id name="id" column="id">
<generator class="foreign">
<param name="property">person</param>
</generator>
<!-- <generator class="native"/> -->
</id>
<property name="name" column="name" />
<one-to-one name="person" constrained="true" lazy="proxy" fetch="join"/>
<!-- <many-to-one name="person" column="person_id" unique="true"/> -->
</class> </hibernate-mapping>
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.dzq.domain"> <class name="Person" table="person">
<id name="id" column="id">
<generator class="native" />
</id>
<property name="name" column="name" />
<one-to-one name="idcard"/>
<!-- <one-to-one name="idcard" property-ref="person"/> -->
</class> </hibernate-mapping>
多对一懒加载（影响性能，最好不禁用懒加载，使用hibernate初始化代理，解决）
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.dzq.domain"> <class name="Department" table="department">
<id name="id" column="id">
<generator class="native" />
</id>
<property name="name" column="name" />
<!-- <set name="empls" cascade="save-update">
<key column="depart_id"/>
<one-to-many class="Employee"/>
</set> -->
<set name="empls" inverse="true">
<key column="depart_id"/>
<one-to-many class="Employee"/>
</set>
<!-- <list name="empls">
<key column="depart_id"/>
<list-index column="order_col"/>
<one-to-many class="Employee"/>
</list> --> <!-- <bag name="empls">
<key column="depart_id"/>
<one-to-many class="Employee"/>
</bag>
--> </class> </hibernate-mapping>
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.dzq.domain"> <class name="Employee" table="employee" discriminator-value="0">
<id name="id" column="id">
<generator class="hilo" />
</id>
<!-- <discriminator column="type"/> -->
<property name="name" column="name" />
<many-to-one name="depart" column="depart_id" />
<!-- <subclass name="Skiller" discriminator-value="1">
<property name="skiller"/>
</subclass>
<subclass name="Sales" discriminator-value="2">
<property name="sell"/>
</subclass> -->
<!-- <joined-subclass name="Skiller" table="skiller">
<key column="emp_id"/>
<property name="skiller"/>
</joined-subclass>
<joined-subclass name="Sales" table="sales">
<key column="emp_id"/>
<property name="sell"/>
</joined-subclass> -->
<!-- <subclass name="Skiller" discriminator-value="1">
<property name="skiller"/>
</subclass>
<subclass name="Sales" discriminator-value="2">
<join table="sales">
<key column="emp_id"/>
<property name="sell"/>
</join> </subclass> -->
<union-subclass name="Skiller">
<property name="skiller"/>
</union-subclass>
<union-subclass name="Sales">
<property name="sell"/>
</union-subclass>
</class> </hibernate-mapping>
public static Department queryDepart(int id){
Session s=null;
try{
s=HibernateUntils.getSession();
Department depart=(Department) s.get(Department.class, id);
Hibernate.initialize(depart.getEmpls());//hibernate初始化代理
System.out.println(depart.getEmpls().getClass());
return depart;
}finally{
if(s!=null){
s.close();
}
}
}
多对多懒加载（（更加影响性能，最好不禁用懒加载，使用hibernate初始化代理，解决））