Hibernate 一对多例-优快云博客

本文链接：https://blog.youkuaiyun.com/zhenyang2002/article/details/405352

博客展示了使用Hibernate实现用户与房间一对多关系的示例。包含SQL创建房间和用户表，定义User和Room类，配置对应的hbm.xml文件，还给出了测试代码，通过Hibernate完成数据的保存操作，数据库使用MySQL。

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SQL(数据库使用的MySQL)：
CREATE TABLE room (
ROOM_ID int NOT NULL auto_increment,
ADDRESS varchar(32) NOT NULL default '',
PRIMARY KEY (ROOM_ID)
) TYPE=INNODB;
CREATE TABLE user (
USER_ID int NOT NULL auto_increment,
NAME varchar(16) NOT NULL default '',
ROOM_ID int NOT NULL default '',
INDEX (ROOM_ID),
FOREIGN KEY (ROOM_ID) REFERENCES Room(ROOM_ID),
PRIMARY KEY (USER_ID)
) TYPE=INNODB;

User.java
package ivan.hibernate.one2many;
public class User {
    private long id;
    private String name;
    private Room room;
    ...
}

User.hbm.xml
<hibernate-mapping>
    <class name="ivan.hibernate.one2many.User" table="USER">
        <id name="id" column="USER_ID" unsaved-value="0">
            <generator class="increment"/>
        </id>
        <property name="name">
            <column name="NAME" length="16" not-null="true"/>
        </property>
        <many-to-one name="room"
                     column="ROOM_ID"
                     class="ivan.hibernate.one2many.Room"/>
    </class>
</hibernate-mapping>

Room.java
package ivan.hibernate.one2many;
public class Room {
   private long id;
private String address;
   private Set users = new HashSet();
   ...
}

Room.hbm.xml
<hibernate-mapping>
    <class name="ivan.hibernate.one2many.Room" table="ROOM">
        <id name="id" column="ROOM_ID" unsaved-value="0">
            <generator class="increment"/>
        </id>
        <property name="address" type="string"/>
        <set name="users" table="USER" inverse="true" cascade="all">
            <key column="ROOM_ID"/>
            <one-to-many class="ivan.hibernate.one2many.User"/>
        </set>
    </class>
</hibernate-mapping>
//注意这里需要设定 inverse=true。

Test.java
public class Test {
public static void main(String[] args) throws HibernateException {
        SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();

        Room room = new Room();
        room.setAddress("China-10-911");

        User user1 = new User();
        user1.setName("ivan");

        User user2 = new User();
        user2.setName("mada");

        user1.setRoom(room);
        user2.setRoom(room);

        room.getUsers().add(user1);
        room.getUsers().add(user2);

        Session session = sessionFactory.openSession();
        Transaction tx= session.beginTransaction();
        session.save(room);
        tx.commit();
        session.close();

sessionFactory.close();
}
}