自动生成的xml mapping file会根据Student.java和Address.java分别生成两个mapping file，然后在Student的mapping文件中有一个many-to-one的属性。代码如下：

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated 2017-8-24 15:05:51 by Hibernate Tools 3.5.0.Final -->
<hibernate-mapping>
    <class name="hibernate.model.component.Address" table="ADDRESS">
        <id name="postcode" type="java.lang.String">
            <column name="POSTCODE" />
            <generator class="assigned" />
        </id>
        <property name="phone" type="java.lang.String">
            <column name="PHONE" />
        </property>
        <property name="address" type="java.lang.String">
            <column name="ADDRESS" />
        </property>
    </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">
<!-- Generated 2017-8-24 15:05:51 by Hibernate Tools 3.5.0.Final -->
<hibernate-mapping>
    <class name="hibernate.model.Student" table="STUDENT">
        <id name="sid" type="int">
            <column name="SID" />
            <generator class="assigned" />
        </id>
        <property name="sname" type="java.lang.String">
            <column name="SNAME" />
        </property>
        <property name="gender" type="java.lang.String">
            <column name="GENDER" />
        </property>
        <property name="birthday" type="java.util.Date">
            <column name="BIRTHDAY" />
        </property>
        <many-to-one name="address" class="hibernate.model.component.Address" fetch="join">
            <column name="ADDRESS" />
        </many-to-one>
        <property name="picture" type="java.sql.Blob">
            <column name="PICTURE" />
        </property>
    </class>
</hibernate-mapping>