java之hibernate之多对多双向关联映射

1.比如在权限管理中，角色和权限之间的关系就是多对多的关系，表结构为：

2.类结构

Role.java

public class Role implements Serializable{
    private int id;
    private String name;
    private Set<Permission> permissions=new HashSet<Permission>();
    public Role() {
    }
    public Role(String name) {
        super();
        this.name = name;
    }

    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Set<Permission> getPermissions() {
        return permissions;
    }
    public void setPermissions(Set<Permission> permissions) {
        this.permissions = permissions;
    }
}

Permisssion.java

public class Permission implements Serializable{
    private int id;
    private String name;
    private Set<Role> roles;
    public Permission() {
        // TODO Auto-generated constructor stub
    }

    public Permission(String name) {
        super();
        this.name = name;
    }

    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }

    public Set<Role> getRoles() {
        return roles;
    }

    public void setRoles(Set<Role> roles) {
        this.roles = roles;
    }
}

3.映射文件信息

Role.hbm.xml

<hibernate-mapping package="cn.sxt.pojo">
    <class name="Role" table="t_role">
        <id name="id">
            <generator class="native">
            </generator>
        </id>
        <property name="name"/>
        <set name="permissions" table="t_role_permission">
            <!-- 当前类在连接表中的外键 -->
            <key column="rid"></key>
            <many-to-many column="pid" class="Permission"></many-to-many>
        </set>
    </class>
</hibernate-mapping>

Permission.hbm.xml

<hibernate-mapping package="cn.sxt.pojo">
    <class name="Permission" table="t_permission">
        <id name="id">
            <generator class="native">
            </generator>
        </id>
        <property name="name"/>
        <set name="roles" table="t_role_permission" inverse="true">
            <!-- 当前类在连接表中的外键 -->
            <key column="pid"></key>
            <many-to-many column="rid" class="Role"></many-to-many>
        </set>
    </class>
</hibernate-mapping>

4.测试

public class HibernateTest {
    /**
     * 生成数据库表的工具方法
     * */
    @Test
    public void testCreateDB(){
        Configuration cfg = new Configuration().configure();
        SchemaExport se = new SchemaExport(cfg);
        //第一个参数  是否打印sql脚本
        //第二个参数 是否将脚本导出到数据库中执行
        se.create(true, true);
    }
    /**
     * 初始化表数据
     */
    @Test
    public void testInit(){
        Session session = null;
        Transaction tx = null;
        try {
            session = HibernateUtil.getSession();
            tx = session.beginTransaction();
            Permission p1 = new Permission("增加用户");
            Permission p2 = new Permission("删除用户");
            Permission p3 = new Permission("查询用户");
            Permission p4 = new Permission("修改用户");

            Role r1 = new Role("管理员");
            r1.getPermissions().add(p1);
            r1.getPermissions().add(p2);
            r1.getPermissions().add(p3);
            r1.getPermissions().add(p4);
            Role r2 = new Role("vip");
            r2.getPermissions().add(p3);
            r2.getPermissions().add(p4);

            session.save(p1);
            session.save(p2);
            session.save(p3);
            session.save(p4);
            session.save(r1);
            session.save(r2);
            tx.commit();

        } catch (Exception e) {
            if(tx!=null)
                tx.rollback();
        }finally {
            HibernateUtil.close();
        }
    }
    /**
     */
    @Test
    public void testGetData(){
        Session session = HibernateUtil.getSession();
        Role role = (Role)session.get(Role.class, 1);
        System.out.println(role.getId()+"---"+role.getName());
        System.out.println("-------------");
        for(Permission p:role.getPermissions()){
            System.out.println(p.getId()+"---"+p.getName());
        }
        System.out.println("==========================");
        Permission p = (Permission)session.get(Permission.class, 3);
        System.out.println(p.getId()+"----"+p.getName());
        for(Role r:p.getRoles()){
            System.out.println(r.getId()+"---"+r.getName());
        }
        HibernateUtil.close();
    }
}