// 在一的一方创建Set集合

public class User {

    private Integer id;

    private String username;

    private String password;

    private Set<Address> addressSet;

}

//多的一方创建User的对象

public class Address {

    private Integer id;

    private String address;

    private User user;

}

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE hibernate-mapping PUBLIC

    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"

    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.kaishengit.pojo">

    <class name="User" table="user">

        <id name="id">

            <generator class="native"/>

        </id>

        <property name="username"/>

        <property name="password"/>

        <!-- name是类中属性的名字,站在User的角度这是一对多,所以是one-to-many

             然后指定对应的多指的是哪个类.

             <key column="userid"/>指维持这种关系的多的这一端(Address)类对应的表中的外键

             inverse="true"表示放弃关系维护-->

        <set name="addressSet" cascade="delete" inverse="true">

            <key column="userid"/>

            <one-to-many class="Address"/>

        </set>

    </class>

</hibernate-mapping>

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE hibernate-mapping PUBLIC

    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"

    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.kaishengit.pojo">

    <class name="Address" table="address">

        <id name="id">

            <generator class="native"/>

        </id>

        <property name="address"/>

        <!-- 站在这个角度是多对一many-to-one

            name写对应的属性名,class是对应的类 然后指定外键-->

        <many-to-one name="user" class="User" column="userid"/>

    </class>

</hibernate-mapping>

//  方式1

        User u1 = new User();

        u1.setUsername("u1");

        u1.setPassword("aaa");

        Address a1 = new Address();

        a1.setAddress("a1");

        a1.setUser(u1);

        Address a2 = new Address();

        a2.setAddress("a2");

        a2.setUser(u1);

        /* 如果是先save的u1,就能拿到u1的id

        然后再save a1,a2的时候加入外键中,等于执行了3条sql

        如果是先save  a1,a2 那么save的结果是没有userid这个外键的

        在save了u1之后会再去update他们(因为在address关联User的时候,user是*态

        ,当user保存的时候就变成了持久态,User状态发生变化会同步到数据库中,所以address会更新

        ),等于执行了3条sql还有两条update*/

        session.save(u1);

        session.save(a1);

        session.save(a2);

// 所以对于一对多的这种情况,先存1,再存多

 //  方式2 

        User u1 = new User();

        u1.setUsername("u1");

        u1.setPassword("aaa");

        Address a1 = new Address();

        a1.setAddress("a1");

        Address a2 = new Address();

        a2.setAddress("a2");

        Set<Address> set = new HashSet<Address>();

        set.add(a1);

        set.add(a2);

        user.setAddressSet(set);

   // 这样即使是先存1再存多还是5条sql语句 

        session.save(u1);

        session.save(a1);

        session.save(a2);

// 单表查询user

        User user = (User) session.get(User.class, 25);

        System.out.println(user.getUsername());

        /* 要使用address了,单表查询address,这个是延迟查询,当使用address的时候再去查

            ,但是这个查询就必须放在session中才能有作用,给xxx.hbm.xml配置

            lazy="false" 就能取消这个延迟查询,不管你用不用address,但是只要你用user我都会查关联user

            的一切比如(address,这个时候就可以放在session外边了因为查询过后已经放入了内存中*/

        Set<Address> set = user.getAddressSet();

        for(Address a : set) {

            System.out.println(a.getAddress());

        }

    // 或者反过来用address查询,也都是两条单表查询

        Address a1 = (Address) session.get(Address.class, 17);

        System.out.println(a1.getAddress());

        System.out.println(a1.getUser().getUsername());

<set name="addressSet" cascade="delete" inverse="true" fetch="join">

            <key column="userid"/>

            <one-to-many class="Address"/>

        </set>

<set name="addressSet" cascade="delete" inverse="true">

        <key column="userid"/>

        <one-to-many class="Address"/>

</set>

User user = (User) session.get(User.class, 26);

session.delete(user);