Hibernate 学习笔记 之 多对多关系 及其 级联操作

一、多对多配置

User.java

/**
 * Created by Donald on 2016/11/20.
 */
public class User {
    private Integer user_id; //用户id
    private String user_name; //用户名
    private String user_password; //用户密码

    //一个用户可以有多个角色
    private Set setRole = new HashSet();

    public Set getSetRole() {
        return setRole;
    }

    public void setSetRole(Set setRole) {
        this.setRole = setRole;
    }

    public Integer getUser_id() {
        return user_id;
    }

    public void setUser_id(Integer user_id) {
        this.user_id = user_id;
    }

    public String getUser_name() {
        return user_name;
    }

    public void setUser_name(String user_name) {
        this.user_name = user_name;
    }

    public String getUser_password() {
        return user_password;
    }

    public void setUser_password(String user_password) {
        this.user_password = user_password;
    }
}

Role.java

/**
 * Created by Donald on 2016/11/20.
 */
public class Role {
    private Integer role_id;    //角色id
    private String role_name;   //角色名称
    private String role_memo;   //角色描述

    //角色表示多个用户
    private Set setUser = new HashSet();

    public Set getSetUser() {
        return setUser;
    }

    public void setSetUser(Set setUser) {
        this.setUser = setUser;
    }

    public Integer getRole_id() {
        return role_id;
    }

    public void setRole_id(Integer role_id) {
        this.role_id = role_id;
    }

    public String getRole_name() {
        return role_name;
    }

    public void setRole_name(String role_name) {
        this.role_name = role_name;
    }

    public String getRole_memo() {
        return role_memo;
    }

    public void setRole_memo(String role_memo) {
        this.role_memo = role_memo;
    }
}

User.hbm.xml

<hibernate-mapping>
    
    <class name="com.yyf.manytomany.User" table="t_user">
        <id name="user_id" column="user_id">
            <generator class="native">generator>
        id>
        <property name="user_name" column="user_name" >property>
        <property name="user_password" column="user_password">property>

        <set name="setRole" table="user_role">

            <key column="userid">key>
            
            <many-to-many  class="com.yyf.manytomany.Role" column="roleid"/>
        set>
    class>
hibernate-mapping>

Role.hbm.xml

<hibernate-mapping>
    
    <class name="com.yyf.manytomany.Role" table="t_Role">
        <id name="role_id" column="role_id">
            <generator class="native">generator>
        id>
        <property name="role_name" column="role_name" >property>
        <property name="role_memo" column="role_memo">property>


        <set name="setUser" table="user_role">

            <key column="roleid">key>

            <many-to-many  class="com.yyf.manytomany.User" column="userid"/>
        set>
    class>
hibernate-mapping>

---

二、级联操作—-保存

若无save-update则保存不成功。

测试：

/**
     * 添加两个用户，为每个用户添加两个角色
     */

    @Test
    public void testSave() {
        SessionFactory sessionFactory = null;
        Session session = null;
        Transaction tx = null;
        try{
            sessionFactory = HibernateUtils.getSessionFactory();
            session = sessionFactory.openSession();
            tx = session.beginTransaction();

            User user1 = new User();
            user1.setUser_name("lucy");
            user1.setUser_password("123");

            User user2 = new User();
            user2.setUser_name("mary");
            user2.setUser_password("456");

            Role role1 = new Role();
            role1.setRole_name("总经理");
            role1.setRole_memo("总经理");

            Role role2 = new Role();
            role2.setRole_name("秘书");
            role2.setRole_memo("秘书");

            Role role3 = new Role();
            role3.setRole_name("保安");
            role3.setRole_memo("保安");

            //2. 建立关系，把角色放到用户里面
            //user1 ----r1/r2
            user1.getSetRole().add(role1);
            user1.getSetRole().add(role2);
            //user2 ----r2/r3
            user2.getSetRole().add(role2);
            user2.getSetRole().add(role3);

            //3.保存用户
            session.save(user1);
            session.save(user2);

            tx.commit();
        }catch (Exception e){
            tx.rollback();
        }
    }

---

三、级联操作—-删除

这种删除会将关联的所有的数据删除

@Test
    public void testDelete2() {
        SessionFactory sessionFactory = null;
        Session session = null;
        Transaction tx = null;
        try{
            sessionFactory = HibernateUtils.getSessionFactory();
            session = sessionFactory.openSession();
            tx = session.beginTransaction();

            User user = session.get(User.class, 3);
            session.delete(user);

            tx.commit();
        }catch (Exception e){
            tx.rollback();
        }
    }

---

四、级联操作—-维护第三张表

其实主要操作set

   /**
     * 1.用户和角色多对多关系，维护关系通过第三张表维护
     *
     * 2.让某个用户有某个角色
     * ① 根据id查询用户和角色
     * ②把角色对象放到用户set集合
     *
     * 3.让某个用户没有某个角色
     * ①根据id查询用户和角色
     * ②从用户里面把角色去掉
     *
     */
    @Test
    public void testOperator() {
        SessionFactory sessionFactory = null;
        Session session = null;
        Transaction tx = null;
        try{
            sessionFactory = HibernateUtils.getSessionFactory();
            session = sessionFactory.openSession();
            tx = session.beginTransaction();

            /**
             * 让某个用户有某个角色
             * 让lucy有经纪人角色
             *
             * 1.查询lucy和经济人
             * 2.放入user的set里
             */

//            User lucy = session.get(User.class, 1);
//            Role role = session.get(Role.class, 1);
//
//            lucy.getSetRole().add(role);

            /**
             * 删除操作
             */
            User user = session.get(User.class, 4);
            Role role = session.get(Role.class, 3);

            user.getSetRole().remove(role);

            tx.commit();
        }catch (Exception e){
            tx.rollback();
        }
    }