hibernate多对多操作

最新推荐文章于 2023-04-05 17:31:32 发布

原创最新推荐文章于 2023-04-05 17:31:32 发布 · 83 阅读

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本文介绍使用 Hibernate 框架实现多对多关系的方法。通过 SQL 创建基础表结构，并定义 Java 类与映射文件来关联 tgroup 和 trole 表。演示了如何在 Group 和 Role 对象间建立联系并保存到数据库。

SQL(MY SQL):

create table tgroup (

group_id int not null auto_increment,

name varchar(16) not null default '',

primary key (group_id)

) type=innodb;

create table trole (

role_id int not null auto_increment,

name varchar(16) not null default '',

primary key (role_id)

) type=innodb;

create table tgroup_role (

group_id int not null,

role_id int not null,

primary key(group_id, role_id),

index (group_id),

foreign key (group_id) references tgroup(group_id),

index (role_id),

foreign key (role_id) references trole(role_id)

) type=innodb;

Group 类：

package ivan.hibernate.many2many;

public class Group {

private int id;

private String name;

private Set roles = new HashSet();

...

}

Group.hbm.xml：

<hibernate-mapping>

</id>

<set name="roles"

table="tgroup_role"

cascade="save-update">

<many-to-many class="ivan.hibernate.many2many.Role"

column="role_id"/>

</set>

</class>

</hibernate-mapping>

Role 类：

package ivan.hibernate.many2many;

public class Role {

private int id;

private String name;

private Set groups = new HashSet();

...

}

Role.hbm.xml：

<hibernate-mapping>

</id>

<set name="groups"

table="tgroup_role"

inverse="true"

cascade="save-update">

<many-to-many class="ivan.hibernate.many2many.Group"

column="group_id"/>

</set>

</class>

</hibernate-mapping>

hibernate.cfg.xml

public class Test {

public static void main(String[] args) throws HibernateException {

Role role1 = new Role();

role1.setName("Role1");

Role role2 = new Role();

role2.setName("Role2");

Role role3 = new Role();

role3.setName("Role3");

Group group1 = new Group();

group1.setName("group1");

Group group2 = new Group();

group2.setName("group2");

Group group3 = new Group();

group3.setName("group3");

group1.getRoles().add(role1);

group1.getRoles().add(role2);

group2.getRoles().add(role2);

group2.getRoles().add(role3);

group3.getRoles().add(role1);

group3.getRoles().add(role3);

role1.getGroups().add(group1);

role1.getGroups().add(group3);

role2.getGroups().add(group1);

role2.getGroups().add(group2);

role3.getGroups().add(group2);

role3.getGroups().add(group3);

SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();

Session session = sessionFactory.openSession();

Transaction tx= session.beginTransaction();

session.save(role1);

session.save(role2);

session.save(role3);

session.save(group1);

session.save(group2);

session.save(group3);

tx.commit();

session.close();

sessionFactory.close();

}